An Australian man who travelled to Syria to join Kurds battling Islamic State jihadists has been killed in battle, the first Westerner to die fighting alongside the Kurds, a monitor says.

"An Australian man was killed in an assault on Tuesday by the Islamic State against a position of the Kurdish People's Protection Units (YPG) near Tal Hamis in Hasakeh province," said Rami Abdel Rahman, the director of the Syrian Observatory for Human Rights.

The Observatory had reported the fighter's death on Tuesday, but was unable to confirm his nationality until Wednesday.

Fairfax Media spoke to a Kurdish Syrian translator, Sabry Omar, who saw the Australian on Mount Sinjar in Iraqi Kurdistan last month.

"He was on the frontline when he was injured - I saw him in hospital, but he was not seriously hurt," he said. "A suicide bomber in a car exploded near him and his eyes were injured."