BEIRUT - The Islamic State group used poison gas in attacks against Kurdish-controlled areas of northeastern Syria in late June, a Syrian Kurdish militia and a group monitoring the Syrian conflict said on Saturday.The YPG militia said Islamic State had fired "makeshift chemical projectiles" on June 28 at a YPG-controlled area of the city of Hasaka, and at YPG positions south of the town of Tel Brak to the northeast of Hasaka city.Redur Xelil, the YPG spokesman, said the type of chemical used had not been definitively determined. None of the YPG fighters exposed to the gas had died because they were quickly taken to hospital, he said.It was the first time Islamic State had used poison gas against the YPG, he added.The Syrian Observatory for Human Rights, a UK-based group that reports on the war using an activist network on the ground, said it had also documented the use of poison gas by Islamic State in an attack on a village near Tel Brak on June 28.It said 12 YPG fighters had been exposed to the gas. The Observatory also said it had received information about the gas attack on Hasaka city, but gave no further details.Reports of poison gas attacks by the Islamic State group could not be independently verified by Reuters. The YPG statement said it was investigating Islamic State's use of chemical weapons with help from an international team of experts. The YPG has driven Islamic State from wide areas of northeastern Syria this year with the help of U.S.-led air strikes. Areas captured from Islamic State include the town of Tel Abyad at the border with Turkey.In a statement, the YPG said its forces had captured industrial grade gas masks in the last four weeks from Islamic State fighters, "confirming that they are prepared and equipped for chemical warfare along this sector of the front".It said soldiers exposed to the gas "experienced burning of the throat, eyes and nose, combined with severe headaches, muscle pain and impaired concentration and mobility". "Prolonged exposure to the chemicals also caused vomiting," it added.