Australian Foreign Minister Bob Carr on Friday issued a warning to Australians registered as being in Syria to leave the country immediately, "ahead of any international response to last week's suspected chemical weapons attack in Damascus".

The foreign minister said there are 59 Australians registered as being in Syria. "Our message to these 59 Australians, including up to 6 children, is to leave Syria by road or air while it is still possible to do so," Carr said in a statement.

"Australians, particularly families with children, should exit Syria as soon as possible."

Carr also confirmed "the risk of further violence is very high and there is no margin for safety in Damascus, Aleppo or any other city in Syria".

Prime Minister Kevin Rudd said Thursday Australia condemned the Syrian regime for using chemical weapons on its own people.

Echoing comments by U.S. President Barack Obama earlier Thursday, Rudd said the evidence is "overwhelming" that the regime of Bashar al-Assad is behind last week's chemical attack in the suburbs of Damascus which killed hundreds of people in a "flagrant breach of international law".

"It is an offence against humanity and arguably is a crime against humanity, "he told a news conference on Thursday. " Therefore, it is now critical that the international community move towards agreement on a robust international response to the regime."

On Tuesday morning, Kevin Rudd "discussed how to chart a way forward" with U.S. President Barack Obama by phone. And the White House has released a statement about the telephone conversation, saying "the two leaders expressed their grave concern about the reported use of chemical weapons by the Syrian regime against civilians".