A day after the deadly attacks on three subway trains and a public bus, tourists were starting to use the Tube again to visit London's tourist attractions.

Flags flew at half mast outside several London embassies on Friday as the death toll from the rush-hour bombings rose to more than 50.

Security was heightened especially around the US embassy which is guarded by police carrying heavy machine guns.

Visitors from China, Sierra Leone, Portugal, Australia and Poland were injured in the four blasts.

The Australian Ambassador to Britain Richard Alston says nine Australians were injured with two in a critical condition.

But Alston said a downturn in Australian visitors was highly unlikely as many feel the UK is their second home.

"Although there was a significant downturn in the flow of holiday traffic to Bali following the bombings I would have thought people would still come to London in the way they always have. There are usually over 100-thousand Australians in London at any one time. Many people regard as London as their second home so I don't think we'll see too much of a downturn."

Experts point to the succesful recovery of tourism following the terrorist attacks in New York and Madrid.

They believe the impact on one of Britain's major industries will be short-term.

However it will take some time for both locals and visitors to recover from the shock. The usually bustling Trafalgar Square was nearly empty on Friday.