Britain has asked Moscow to hand over any information it has that could help with the UK police investigation into the death of ex-KGB spy Alexander Litvinenko, a Foreign Office spokeswoman said tonight.
"(Foreign Office) officials discussed the death of Mr Litvinenko with the Russian Ambassador this afternoon ... The situation was now more serious with Mr Litvinenko's death," the spokeswoman told Reuters.
"The Ambassador was asked to convey to the authorities in Moscow to provide any information they might have that would assist the police with their inquiries."
British police investigating the death have found levels of radiation in a London sushi bar where he ate just before he became sick, health officials said earlier.
The police reported that they had found some radiation there (in the Sushi bar). We are assessing the level of that and the potential risk to people that might cause," Pat Troop, head of the independent Health Protection Agency, told the BBC.
The HPA said polonium 210, a radioactive isotope, had been discovered in the body of Alexander Litvinenko, who died overnight at a London hospital after wasting away during three weeks of illness.
British Home Secretary John Reid
As detectives and specialist experts began a hunt for traces of the radiation, Mr Litvinenko's family released his deathbed statement, pointing the finger of blame for his killing at Russian president Vladimir Putin.
But Mr Putin hit back at the allegations, insisting there was no proof that Mr Litvinenko's death was "violent".
Speaking for the first time since Mr Litvinenko's death at University College Hospital, the Russian President said: "As far as I understand from the medical statement, it does not say this was the result of violence, this was not a violent death."
The
British
Home Secretary John Reid said the death of Mr Litvinenko was "believed to be linked to the presence of a radioactive substance in his body".
"As part of this investigation, the police have called in expert assistance to search for any residual radioactive material at a number of locations," Mr Reid said in a statement.
Mr Litvinenko's deathbed statement said of Mr Putin: "You have shown yourself to be as barbaric and ruthless as your most hostile critics have claimed.
"You may succeed in silencing one man, but the howl of protest from around the world will reverberate, Mr Putin, in your ears for the rest of your life.
"May God forgive you for what you have done, not only to me, but to beloved Russia and its people."