The United Nations' chemical weapons watchdog is looking into allegations that Turkish forces fired non-conventional weapons on Kurdish forces in northern Syria.
The organisation said that although it has not launched a formal investigation, it would try to collect information with regards to claims that Turkey used chemicals such as napalm and white phosphorus during its Operation Peace Spring against Kurdish forces.
"[The Organisation for the Prohibition of Chemical Weapons] experts are engaged in the process of assessing the credibility of allegations concerning the situation in northern Syria," a statement said.
Ankara has denied the charges.
OPCW specialists continue to collect information "with regard to any alleged use of chemicals as a weapon," the watchdog group said.
The Syrian Observatory for Human Rights, which has a network of Syrian sources, said it could not confirm the use of chemical weapons, but that Kurdish fighters suffering from burns were treated in a hospital in Tal Tamr, near the border town of Ras Al Ain that was bombarded by pro-Turkish forces.
The use of chemical weapons, including substances similar to napalm and phosphorous has been alleged many times since the Syrian conflict began in 2011.
The Kurdish Red Crescent said that six patients, both civilian and military, were in hospital in Hasakah with burns from "unknown weapons" and it was working to evaluate what had been used.
It said it could not confirm the use of chemical weapons and was “working together with our international partners to investigate this subject”.
Kurdish authorities also posted images on social media that showed children suffering from burns that a local doctor said might have been caused by chemical substances.
On Wednesday, US President Donald Trump's special envoy for Syria said that US forces had seen evidence of war crimes by Turkish forces during their recent offensive against Kurds in Syria.
"We haven't seen widespread evidence of ethnic cleansing" by Turkey, but there had been reports of "several incidents of what we consider war crimes," said James Jeffrey, special representative for Syria, at a House of Representatives hearing.
He said US officials were looking into those reports and had demanded an explanation from Turkey's government, and investigating a report that Turkey had used restricted burning white phosphorus during its offensive.
Hulusi Akar, Turkish defence minister, said: “It is a fact known by everyone that there are no chemical weapons in the inventory of the Turkish armed forces.”
Syrian President Bashar Al Assad on Tuesday denounced Turkish leader Recep Tayyip Erdogan as a thief for attacking the north-east of his country and again pledged to retake all areas lost to Damascus in years of civil war.
Mr Al Assad made a rare visit to front lines in north-western Idlib province, near the last major bastion of Turkey-backed rebel forces.