Alexander Downer: "It's a tragedy"

Sam Ly, from Melbourne, was a passenger on board the bus that was targeted in Tavistock Square.

Mr Downer said he did not know whether Mr Ly had ever regained consciousness.

He was one of 10 Australians injured in the bombings, which also saw three underground trains hit by rush-hour bomb explosions on 7 July.

"It's a tragedy that an Australian should be amongst those who have been killed in London, but you can rest assured that the Australian government will do all it can to assist the British... to track down the whole network that is responsible for this appalling act," Mr Downer told reporters.

"It does remind us that the struggle against terrorism is a global struggle, it's not just something confined to one region... and that all countries have to make some commitment to defeating terrorism."

Bedside vigil

A total of 51 people are known to have been killed by the bombers. Three of the attackers are also confirmed to have died, and the fourth is believed dead.

The only Australian known to have been killed in the bombings, Mr Ly had recently moved to London with his girlfriend to work in the IT industry.

His father and nephew had flown to London to be at his bedside.

One other Australian remains in a critical condition in a London hospital.

In the wake of the bombings, Australian Prime Minister John Howard said Australians felt a particular sympathy for the British because of a connection going back generations.

Some 300,000 Australians currently live and work in the UK, most of them in London.