Prime Minister Julia Gillard has condemned the "brutal" terrorist attack at Moscow airport.
At least 35 people were killed and more than 140 wounded in the bombing at Domodedovo Airport, Russia's busiest.
"This brutal attack appears to have killed many and injured more, and the thoughts of Australians are with the families of all those who have suffered as a result of this act," Ms Gillard said in a statement.
She offered Australia's condolences to Russia and other nations affected by the "appalling and indiscriminate act of violence".
Department of Foreign Affairs and Trade (DFAT) officials in Moscow were working hard to determine if any Australians were caught up in the blast, she said.
A Briton and other foreigners reportedly were among those killed.
DFAT has advised concerned family and friends to try to make direct contact with anyone they fear may have been at the airport at the time of the bombing.
"If you are unable to contact them and still hold concerns for their welfare, you should call the Department of Foreign Affairs and Trade's 24-hour Consular Emergency Centre on 1300 555 135," the department said.
The department also advised Australians in Russia to exercise caution.
"Russian authorities continue to warn of the possibility of further terrorist attacks in Moscow," it said.
Russian authorities have established a hotline for concerned friends and relatives seeking information.
The numbers are (+7 495) 363 6101; (+7 495) 662 8247 and (+7 495) 644 4056.
Defence Minister Stephen Smith said the "terrible atrocity" was a feature of modern life.
"We are, of course, primarily concerned about any adverse consequences for Australians," he told the ABC.
An Australian man identified as Ben said he was just about to enter the arrivals hall when the explosion occurred.
"We heard the explosion first and heard a very, very large bang," he told ABC Radio.
"We thought it might be a construction accident but couldn't figure out what that might be, and we saw clouds of dust coming out from that area.
"The blast was loud enough and strong enough that it shook the walls around us."
British passenger Mark Green said he was exiting the arrivals hall when the blast occurred.
"There was this almighty explosion, a huge bang," he told ABC
Radio.
"My colleague and I thought it was a car bomb or something because the explosion shook you.
"We could see confused people moving around and clouds and clouds of dust coming out of that area.
"There was a huge amount of people flooding out of the terminal building ... we didn't realise it was a terrorist attack at that point."
