Prime minister Malcolm Turnbull has condemned the London terror attack on Friday, calling it "criminal and callous" and expressing his sympathy.
At least 29 people were injured when an explosive device was set off on a carriage at Parsons Green underground station on Friday morning UK time.
ISIS has claimed responsibility for the attack, which has seen the UK's threat level raised to "critical".
Turnbull expressed his sympathy on a message on Facebook.
"On behalf of all Australians, I condemn the terrorist attack on a train at the Parsons Green Station in London," he wrote on Saturday afternoon.
"This is yet another criminal and callous attack on Londoners going about their daily lives. My heartfelt sympathy is with all those affected.
"UK Police have declared it a terrorist-related incident and confirmed it involved an improvised explosive device causing flash burns.
29 people are reported injured but thankfully at this stage none are believed to be in a serious or life-threatening condition. We know only too well that London’s first responders will be doing everything they can to look after those affected."
He confirmed Australia's threat level remains at "probable".
"My number one priority, and that of my Government, is to keep Australians safe and to preserve our freedoms and our way of life," he said.