The Federal Government is working to verify reports an Australian man has been killed in Syria, believed to be the third Australian death over the past month.

A spokesman for the Department of Foreign Affairs and Trade said it was investigating, but that verifying the reports was difficult.

There have been three unconfirmed reports of Australian Islamic State (IS) fighters being killed since mid October, including the Western Sydney actor turned Islamic State recruiter Mohammad Ali Baryalei.

Baryalei had been accused of masterminding a plot to kill random members of the public in Sydney and Brisbane, and had recruited dozens of Australians to fight with extremist groups in Iraq and Syria.

The 33-year-old from Sydney was the catalyst for September's unprecedented counter-terrorism raids, when more than 800 police raided homes in Sydney and Brisbane and charged four people.

Baryalei was said to hold a trusted position in Islamic State's operational command and to have facilitated the recruitment of at least half of the 60 Australians currently fighting in the Middle East.

But authorities said they had no evidence confirming Baryalei's death, and have expressed caution.

The news also followed the confirmed death of Queensland man Zia Abdul Haq last month, after he travelled to Syria to fight for the fundamentalist group.

Consular assistance is no longer available in Syria or Iraq and the government is warning against travel to the two countries.