Police say three of the four bombers thought to have died in the attacks are included in this figure.
Scotland Yard said on Thursday a man had died in the National Hospital for Neurology, in Queen Square, London, where he had been taken following the bombing on the Number 30 bus in Tavistock Square.
Earlier on Thursday, people around the UK and the world took part in a two-minute silence to remember those killed and injured a week ago.
Civil rights campaigner Ben Okri told the crowds in Trafalgar Square that London had survived "bombings, burnings and wars" and still grown stronger and more beautiful.
Mr Livingstone told those assembled he was "proud" to be their mayor.
"And out of this tragedy, let us re-double our efforts to build a better city for our children and our grandchildren and lift our hearts, rather than worry about who to blame or who to hate," he said.
Lord Coe, chairman of London's successful 2012 Olympic bid team, said the victims would never be forgotten as London prepared to host the Games.
