Dizzy, vomiting and struggling to breathe, 11 Iraqi police officers were rushed to a government hospital 50 miles north of the capital last month. The diagnosis: poisoning by chlorine gas. The perpetrators, according to the officers: Islamic State extremists. 
 
 The chlorine attack appears to be the first confirmed use of chemical weapons by the Islamic State on the battlefield. An Iraqi Defense Ministry official corroborated the events, and doctors said survivors’ symptoms were consistent with chlorine poisoning. 
 
 Iraqi forces say two other crude chlorine attacks have occurred since the extremists seized vast tracts of Iraqi territory this summer, but details on those incidents remain sketchy. The reported assaults all raise concerns that the militants are attempting to hone their chemical weapons capabilities as they push to control more ground. 
 
 The presence of a large former Iraqi chemical weapons production plant in territory seized by the Islamic State has compounded those fears, although officials and chemical weapons experts say the 2,500 degraded rockets filled with nerve agents that remain there are unlikely to be fit for use. Weapons inspectors sealed them off with concrete in a bunker more than 20 years ago. 
 
 The Islamic State’s reported chlorine attacks appear to have been largely ineffectual. The attack on the police officers last month is the only one officially documented. 
 
 Lt. Khairallah al-Jabbouri, left, and Dr. Hussam Salim, a physician who treated him, after his exposure to chemical weapons, with medical files of the victims. (Loveday Morris/TWP) 
 
 Chlorine, a common component in industry, is sold legally, but its use as a weapon violates the Chemical Weapons Convention. It was widely employed in trench warfare during World War I, including infamously at Ypres in Belgium, where German forces dispersed more than 160 tons of chlorine into the breeze, killing thousands of French and Allied soldiers. 
 
 The Organization for the Prohibition of Chemical Weapons said last month that chlorine gas has been used “systematically” as a weapon in villages in northern Syria. The U.S. government has blamed those attacks on the Syrian government. But it has been years since the chemical has been used in fighting in Iraq. 
 
 ‘It was a strange explosion’ 
 
 It was 4:20 p.m. on Sept. 15 when the 11 police officers were rushed into the hospital emergency room in Balad. Some struggled to stand; tears streamed from their eyes. 
 
 “They were panicked; we were panicked,” said Kasim Hatim, the hospital’s director. “We initially thought it might be a more serious gas, a nerve gas or an organophosphate.” 
 
 The men had been brought in from the front lines of the nearby town of Duluiyah. Tucked into a bend of the Tigris River, the town had been under heavy assault for days, according to the accounts of three survivors. Islamic State fighters had taken territory to the north, cutting the only direct land access to the river town, and had blown up the last bridge into the town. 
 
 The police officers, all members of the Sunni Jabbour tribe, which has turned against the Islamic State, were guarding a line in the town’s north. After an exchange of fire, they said, they were surprised to see Islamic State fighters retreating from their position about 150 yards away. 
 
 Suddenly there was a boom in the area the extremists had just vacated, said Lt. Khairalla al-Jabbouri, 31, one of the survivors. “It was a strange explosion. We saw a yellow smoke in the sky,” he said. The wind carried the fog toward their lines. The men say it hung close to the ground, consistent with the properties of chlorine gas, which is heavier than air. 
 
 “I felt suffocated,” Jabbouri recalled. “I was throwing up and couldn’t breathe.” 
 
 Another officer, Ammer Jassim Mohammed, 31, who suffers from asthma, said he passed out within minutes. 
 
 The men were taken to a small clinic in Duluiyah, before being transferred by boat to the larger hospital in Balad, where they were treated with oxygen and hydrocortisone, an anti-inflammatory medication, until the symptoms began to subside. They were all discharged the following morning. 
 
 The four physicians who treated them said there was no question that chlorine gas was to blame. 
 
 One physician on the team, Hassanain Mohammed, had treated similar cases­ before. In 2006 and 2007, al-Qaeda in Iraq, a group that later morphed into the Islamic State, carried out a string of chlorine bombings in the country. 
 
 Mohammed was on duty at a Baghdad hospital one day during that period when dozens of victims were brought in after a bombing in Taji district, just north of the capital, in which insurgents had packed a truck with explosives and two one-ton chlorine tanks. 
 
 There have been no confirmed accounts of the use of chlorine gas as a weapon in Iraq for several years. 
 
 An Iraqi Defense Ministry official confirmed this week that a bomb rigged with chlorine canisters was used in the Duluiyah attack. 
 
 “They use it just to create terror,” said the official, who spoke on the condition of anonymity because he was not authorized to provide the information publicly. “But of course we are very concerned.” 
 
 In a statement, the Defense Ministry confirmed that the Islamic State has used the gas in a “primitive and ineffective way” near water-treatment plants where it has gained access to chlorine, as well as in roadside bomb attacks. It did not specify the locations of the attacks, but there are several water plants near Duluiyah on territory controlled by the Islamic State. 
 
 The extremist group aims to dent “the morale of the Iraqi people in general and our armed forces­ in particular,” the statement said. 
 
 It said that soldiers should be provided with gas masks as a precaution and that volunteers and civilians should place a dampened cloth over the nose and mouth to protect themselves during any attacks. 
 
 The defense official said he did not have details of any incidents other than the Sept. 15 attack, while a U.S. official said he had no reports of the use of chlorine by the Islamic State. 
 
 “We aren’t aware of any chlorine attacks against the [Iraqi security forces­] but would refer you to the Iraqi government to see what they might have,” said Army Maj. Curtis Kellogg, a spokesman for Florida-based U.S. Central Command, which is responsible for U.S. security interests in the Middle East. 
 
 An inexact weapon 
 
 Chlorine bombs are an easy-to-create but inexact weapon, experts say. All that is needed is a small explosive charge to rupture containers filled with the substance. 
 
 “It’s difficult to deliver on target in combat situations,” said Jean Pascal Zanders, an independent researcher who specializes in chemical and biological weapons and disarmament. “Chlorine dissipates fast unless someone is able to concentrate it in a confined area.” 
 
 Fighters in Duluiyah say it was not the only time chlorine has been used against them. Another attack this month caused minor injuries, and the fighters were treated locally, police officials said. 
 
 Immediately after the September attack, the Balad hospital put in orders for thousands of doses of atropine, used to treat nerve-gas exposure, Hatim said. A thousand have been shipped across the river to Duluiyah. 
 
 Soldiers who escaped an Islamic State rout of a besieged army base in Saqlawiyah, where hundreds of soldiers were killed last month, also said chlorine gas was used there — though reports of where and how the gas was delivered varied and could not be confirmed. 
 
 While some officers said they believed artillery- or mortar-launched canisters fired by the attackers fell short of the base, others, who claimed to have remained in the installation for a longer period, said the canisters fell within its perimeter. Another claimed that the militants detonated chlorine-filled containers. 
 
 “It was chaos,” said Capt. Ahmed Hussein. He said he believed that gas canisters were fired into the camp but pointed out that the situation was highly confused. “I saw an explosion and smelled the smell; it was like bleach,” he said. “I was far enough away, but others were affected and were left behind.” 
 
 Ammar Toma, a member of parliament’s defense and security committee, said the panel had received photographs from officers of the projectiles used in the Saqlawiyah area. 
 
 “We aren’t sure chlorine was used,” he said. “But we believe it was either chlorine or another chemical.” 
 
 Mustafa Salim in Balad and Karen DeYoung in Washington contributed to this report. ||||| Kurds battling Islamic State militants for control of Kobani fear the extremist group may have used an unidentified chemical weapon, according to officials and one of the few doctors still working in the besieged Syrian town. 
 
 Patients with blisters, burning eyes and breathing difficulties turned up at a clinic after a blast was heard on Tuesday evening, Dr Walat Omar said. He described the symptoms as abnormal and said he could not identify their cause, but suspected a chemical weapon. 
 
 “After a loud explosion [on Tuesday night], we received some patients with abnormal symptoms. They reported a bad smell which produced some kind of allergic reaction,” Omar said in a telephone interview that was periodically disrupted by heavy explosions. 
 
 Facebook Twitter Pinterest Blisters on the body of a man in Kobani which Kurds fear may have been caused by Islamic State’s use of a chemical weapon. The Guardian is unable to ascertain the cause of the blisters. Photograph: Walat Omar 
 
 “Some had red patches and blisters on their skins, others had difficulties breathing and others were vomiting, with painful throats, and others with burning eyes and noses. There was one patient, all his body was covered in red patches and blisters.” 
 
 Islamic State (Isis) is thought to have obtained stocks of ageing but still potent chemical weapons when it seized Iraqi army bases where they were stored, the New York Times reported earlier this month. 
 
 In June, the group took control of a sprawling complex that had been the heart of Saddam Hussein’s chemical weapons programme, Al-Muthanna State Establishment. There may also have been chemical weapons buried or abandoned elsewhere, that were not destroyed by US forces or the Iraqi military. 
 
 Stocks manufactured before 1991 are dirty, corroded and not always easy to identify or use, but can still cause serious injury. 
 
 Iraqi officials said 11 police officers were poisoned by chlorine gas last month, when Isis fighters used it to attack the Iraqi town of Duluiya. All the officers survived. 
 
 That attack was hundreds of miles from Kobani, near the Syrian border, where Omar said he feared eight civilians had been injured by some kind of chemical attack. 
 
 Intense fighting has made it impossible to get doctors the equipment they need to do definitive tests for the use of chemical weapons, but Omar said they displayed symptoms distinct from anything else he had treated in weeks of heavy battles. 
 
 He said he had ruled out chlorine gas or biological weapons, based on his medical training, but thought the injuries were caused by a chemical. Trained in Ukraine, he is originally from Kobani and returned there to work after seven years at medical school. 
 
 “This is the first time we have seen this kind of condition,” Omar said. “I have seen other strange conditions but nothing like this before.” 
 
 The opinions of chemical weapons experts consulted by the Guardian were divided after seening a series of pictures provided by Omar of a young man with large skin blisters and a severely swollen lip. 
 
 The pictures did not have any metadata to confirm the time and place they were taken, but had not been published on the internet before Omar provided them to a Kurdish journalist. 
 
 One expert with personal experience of treating mustard gas victims said that, although the blisters were not typical, the symptoms overall were consistent with a possible sulphur mustard poisoning. That could only be confirmed with a urine or blood test. 
 
 Other experts said that while the symptoms could be consistent with exposure to a chemical agent, they were somewhat unusual and other medical conditions, such as a severe allergic reaction, would need to be ruled out. 
 
 Senior Kurdish politicians said they feared a chemical attack, and had asked for testing kits to seek confirmation. 
 
 “Many people were injured … and showed symptoms of chemical weapons use: choking, breathing difficulties, bleeding eyes, burning skin etc,” said Idris Nassan, deputy foreign minister of the Kobani administration. “Some of the doctors say that it might be phosphorus or poison gas of some kind, but the investigation is ongoing, we don’t know for sure.” 
 
 It is possible that Isis fighters could mistake some chemical munitions for ordinary weapons and use them without being aware of what they are handling. It could also be harder to evaluate the impact of attacks using partially degraded weapons, one expert said. 
 
 “Various factors might contribute to far milder symptoms than those normally associated with mustard agent exposure under combat conditions. These could include impure or degraded agent, short-term exposure, or exposure to a limited volume of agent,” said Jean-Pascal Zanders, a former analyst with the chemical and biological warfare project at the Stockholm International Peace Research Institute. 
 
 The bomb believed to have caused the injuries treated by Omar exploded at about 10pm in west Kobani, near a hospital. Omar said he thought Isis may have targeted the medical centre to try to undermine morale, although it was not being used and none of the forces defending the city were in the area. 
 
 “Some fighters were further away, they complained about their eyes watering and burning, and pain in their nose,” he said, estimating that around 20 of them were affected but needed only basic first aid. 
 
 Regarding civilians who were closer to the blast, Omar said he was treating affected patients with oxygen, the steroid cortisone and other drugs until about 2.30am, as well as fielding calls from people who did not want to leave their homes. 
 
 The three most seriously injured patients, who ranged in age from 17 to over 40, stayed in the clinic overnight for observation and Omar was trying to arrange for their evacuation to Turkey for further treatment. 
 
 One Kurdish activist said Kobani may have been hit by teargas for the first time, perhaps drifting across from a Turkish border village where police had been using it for weeks to break up crowds of demonstrators. It has not been deployed in the intense battles for Kobani and so would not be recognised by residents, although demonstrations nearest to the border have almost all been in daylight hours, while Omar reported victims arriving well after nightfall. 
 
 Additional reporting by Constanze Letsch ||||| Image caption Chemical weapons are thought to have been widely used in Syria 
 
 The United States is to investigate whether militant group Islamic State (IS) used chemical weapons in Iraq, Secretary of State John Kerry has said. 
 
 Mr Kerry said he was looking into "extremely serious" allegations that IS attacked Iraqi police officers with chlorine gas last month. 
 
 Speaking on a visit to South Korea, Mr Kerry said the claims were unconfirmed. 
 
 In September, France, Germany and the UK said it was "probable" IS had chlorine gas. 
 
 Mr Kerry said "the use of any chemical weapon is an abhorrent act; it is against international law". 
 
 Choking agent 
 
 It is unlikely that IS possesses serious chemical weapons such as Sarin, VX gas or mustard gas. 
 
 But persistent reports from Iraq say they have been using chlorine gas, which is classed as "a choking agent". 
 
 Though not as deadly as nerve agents, if inhaled in sufficient quantities it can burn victims' lungs as well as generating fear, panic and a high number of casualties. 
 
 The Stockholm International Peace Research Institute (SIPRI) says use of the gas "is a CWC-defined use of chemical weapons." 
 
 CWC stands for the Chemical Weapons Convention, a treaty banning chemical weapons that the many countries have signed. 
 
 It is widely believed that Syrian President Bashar al-Assad used chemical weapons on a large scale. 
 
 To avert the threat of retaliatory Western air strikes, Russia brokered a chemical weapons disarmament deal in January. 
 
 Nevertheless Mr Assad is alleged to have used chlorine gas as recently as August.
– On the heels of reports that ISIS militants are learning to fly fighter jets, Iraqi officials say the group has also used chemical weapons—specifically, chlorine gas. Eleven Iraqi police officers were hospitalized on Sept. 15 after being poisoned by the stuff, according to doctors, and the officers say ISIS was to blame. An Iraqi defense official has confirmed the case, the Washington Post reports. Iraqi security forces have reported two other such attacks, though the details are hazy, the Post notes. Meanwhile, a clinic in Kobani, Syria, received patients suffering from breathing trouble and blisters following the sound of an explosion Tuesday night, the Guardian reports. "Some had red patches and blisters on their skins, others had difficulties breathing and others were vomiting, with painful throats, and others with burning eyes and noses. There was one patient ... all his body was covered in red patches and blisters," says a doctor, who believes a chemical other than chlorine was used in this case. Though chemical weapons have recently been used in Syria, these instances appear to be the first confirmed use of chlorine gas in Iraq in years, the Post reports. The US is investigating the case in Iraq, the BBC reports. All eleven of the officers were discharged from the hospital the next morning.