( CNN ) -- The Turkish government is treating around a dozen patients who have exhibited unusual symptoms suggesting they were exposed to a chemical weapons attack , a Turkish source said . `` They were not injured by any kind of conventional arms . Tests showed excessive results which produced findings to let us make that statement , '' a Turkish source with access to Turkish government findings told CNN , on condition of anonymity due to the sensitivity of the allegations . The Turkish source was referring to an announcement by Turkey 's prime minister which accused the Syrian government of using chemical weapons . `` It is clear the regime has used chemical weapons , '' said Recep Tayyip Erdogan , in an interview broadcast on NBC News Thursday night . `` There are patients who are brought to our hospitals who were wounded by these chemical weapons , '' Erdogan added , speaking through an interpreter . Erdogan said he wanted the US to `` assume more responsibilities and take further steps '' when it comes to Syria . The Turkish leader is expected to travel to Washington next week to hold talks with U.S. president Barack Obama . Erdogan was once a close ally of the Syrian president Bashar al Assad . But he gradually distanced himself from Assad in 2011 , as Syrian security forces mounted an increasingly deadly crackdown on anti-government protesters . Today , Erdogan is an outspoken critic who hs repeatedly demanded Assad step down from office . Turkey hosts more than 190,000 Syrian refugees in state-run camps , as well as many more Syrians who have fled across the border to take shelter in Turkish cities and towns . In addition , Turkey has played a major role providing assistance and a relatively safe springboard for operations to Syrian opposition groups . Ambulances routinely rush war-wounded across the border from Syria to Turkey for treatment in Turkish hospitals . Ankara says it has spent hundreds of millions of dollars housing , feeding and providing medical care to Syrian civilians . The latest accusations by Turkey are not the first time allegations of chemical weapons use have emerged from Syria . The Syrian government and rebels have accused each other of using chemical weapons on the battlefield , prompting the United Nations to call for the deployment of an international team of investigators . This week , in an exclusive interview with CNN 's Frederick Pleitgen , Syrian deputy foreign minister Faisal al-Mekdad declared his government `` would never use '' chemical munitions . He also accused Turkey of supply rebels with chemical weapons . Syrian rebels as well as the Turkish government have denied such allegations , and answered with counter-accusations . Last week , Syrian rebel spokesman Louay al Mokdad claimed opposition fighters had captured an unexploded canister from an alleged chemical weapons attack . Mokdad told CNN he hoped international experts would use the canister as evidence of alleged Syrian government war crimes . The deadly conflict in Syria has repeatedly spilled across borders to Turkey , prompting Turkish security forces to reinforce the frontier . At Turkey 's request , the NATO military alliance deployed several Patriot missile batteries to protect Turkish border cities from the threat of Syrian missile attacks . The Turkish government appears to also be responding to more recent reports of chemical weapons use emerging from Syria . This week , Turkey 's semi-official Anatolian Agency reported that a special chemical , biological , radiation and nuclear research vehicle had been deployed to one of the busiest border gates between Turkey and opposition controlled Syria . READ MORE : Chemical weapons in Syria ? Why Obama still needs convincing . READ MORE : U.S. : Intelligence points to small-scale use of sarin in Syria . READ MORE : Exploring Syria 's chemical weapons stockpile . CNN 's Saad Abedine and Frederick Pleitgen contributed to this report .
The statement comes after an interview by Turkish prime minister . Erdogan, who has been in power for more than a decade, is facing growing criticism over his crackdown on the media and human rights activists. The Syrian government and rebels have accused each other of using chemical weapons in the past .