A foreign fighter believed to be either British or Greek has been killed in Syria while battling the Islamic State group alongside Kurdish militia, a monitor said Tuesday.

The Syrian Observatory for Human Rights said the man died early Tuesday from wounds suffered in a battle with jihadists the day before in the northeastern province of Hasakeh.

Observatory director Rami Abdel Rahman told AFP the fighter was "a European citizen who had been living in Britain, but it is not clear whether he was British or Greek."

He had been fighting with the Kurdish People's Protection Units (YPG), a local militia, in an area southwest of the town of Tal Hamis, which Kurdish fighters seized from IS last week.

No further details about the man's identity were immediately available.