Baghdad ( CNN ) -- A dramatic and bloody outbreak of violence in northern Iraq Tuesday stoked even more agitation in a country simmering with Sunni-Shiite tensions . In northern Iraq , at least 28 people were killed and more than 70 wounded in clashes between security forces and gunmen in Hawija , in Kirkuk province , according to a senior Iraqi army officer who spoke on condition of anonymity because he is not authorized to speak to the media . A senior Interior Ministry official provided similar information on the same condition . Police said the fighting began when security forces looking for wanted people raided al-Atisam Square , the site of ongoing demonstrations by Sunni Muslims . But Sunni politicians claim peaceful Sunni protesters were assaulted during the raid and blame Nuri al-Maliki , the Shiite prime minister . Iraqi House Speaker Osama al-Najafi issued a strong condemnation , saying the army fired on peaceful protesters and calling the military `` a tool to suppress the people and not to defend them . '' `` We condemn in the strongest words of condemnation and denunciation the unfortunate crime committed by the army against the demonstrators in Hawija , '' he said . Al-Maliki ordered an investigation , aid to the wounded , and compensation to their families . Two Sunni Cabinet members -- Minister of Education Mohammed Tameem and Minister of Science and Technology Abdul Karim al-Samarrai -- have submitted their resignations in protest over the actions by security forces , their offices said . Martin Kobler , the U.N. special representative for Iraq , was in Kirkuk to meet with local officials and discuss the Hawija violence , state TV reported . The U.S. Embassy in Baghdad said it is working to `` help defuse political and sectarian tensions '' and it regrets that civilian and security force casualties `` took place before ongoing efforts to reach a peaceful resolution of this situation were given sufficient time to succeed . '' `` All sides should immediately refrain from further violence or provocative actions , '' it said . `` We call for a transparent investigation with the broadest possible participation . '' The situation is now very tense in provinces with large Sunni populations -- such as Anbar , Salaheddin , Nineveh and Diyala , according to the senior Interior Ministry official in Baghdad who also spoke under condition of anonymity . Near the Anbar province city of Falluja , police said , citizens who were angered by the Hawija events set two army vehicles on fire in an attack on an army convoy . One person was killed and another was kidnapped , police said . In a separate attack , a police officer was wounded when a bomb was hurled at a police checkpoint in Falluja , police said . In Tuz Khurmato , in Kirkuk province , at least four Iraqi soldiers were killed and four others wounded when gunmen attacked a security checkpoint . It is not clear if this attack related to the Hawija clashes or sectarian strife . And at least nine people were killed and more than 25 were wounded when three mortar rounds landed on a Sunni mosque in Muqdadiya , a city in Diyala province . Al-Najafi urged security forces and Sunni tribes battling across the country to restrain themselves , warning of a civil war if such fighting continues . Sunni-Shiite tensions . Sunnis , who comprise a minority of Iraqis , had clout during the Saddam Hussein era , but have been politically marginalized since his overthrow . Shiites , who make up a majority of Iraqis , dominate the government . Since December , tens of thousands of demonstrators have taken to the streets of predominately Sunni provinces -- including Anbar , Nineveh , Salaheddin and Diyala -- demanding that the Shiite-led government stop what they call second-class treatment of Iraq 's Sunni community . Such turnouts include protests at al-Atisam Square in Hawija . Over the past few months , al Qaeda in Iraq has claimed responsibility for several attacks across the country that targeted Shiite areas and Iraqi security forces . A number of attacks have targeted the Sunni community in different locations over the past week . The deadliest one was at a popular coffee shop in western Baghdad , which left at least 27 people dead and 51 others wounded . Earlier Tuesday , another attack occurred . At least four people were killed and 13 others were wounded when two roadside bombs exploded , one after another , outside a Sunni mosque in southern Baghdad , police said . The incident occurred in the neighborhood of Dora while Sunni worshipers were leaving the mosque , police said . There was some violence during Saturday 's Iraqi provincial elections , but there were n't major incidents and the polling was considered a success by Iraq , the United States , and the United Nations . CNN 's Joe Sterling contributed to this report .
At least 28 people are killed in a clash in Hawija . Four people are dead in southern Baghdad . Al Qaeda in Iraq has claimed responsibility for some past attacks . A number of attacks have targeted the Sunnis recently .