A YouTube account for a Syrian rebel group shows footage of a man, described as al-Australi ("the Australian"), who the rebels claim died in a battle for control of a major military base.

The man is identified only as Abu al-Walid, a name that means "father of al-Walid" in Arabic.

His identity cannot be confirmed and the Department of Foreign Affairs and Trade says it is unaware of any Australian having died.

The video suggests the man left behind a fiancee to join the fight against the Syrian government, which began in 2011. He is also shown assembling what appears to be an explosive.

Conflict in Syria has been raging between forces loyal to President Bashar al-Assad and the Free Syrian Army.

The two groups have been fighting since October for control of the Wadi Deif military base in the country's north-west.

The rebels have laid siege to the base and the army has responded in turn by raiding rebel positions from the air.

In October a Melbourne man, Roger Abbas, was killed in Syria. He was said to have been caught in a crossfire.