Scotland Yard are now treating the mysterious death of former KGB agent, Alexander Litvinenko, as murder. Two weeks after he succumbed to polonium-210 poisoning, detectives have concluded he was deliberately killed.

In a statement last night, the Metropolitan police said the team investigating Mr Litvinenko's death "have reached the stage where it is felt appropriate to treat it as an allegation of murder".

The statement said "many lines of inquiry, both in the UK and Russia" were being pursued and that detectives were keeping an open mind and "methodically following the evidence".

While Scotland Yard are now ruling out the possibility that Mr Litvinenko deliberately or accidentally poisoned himself, police stressed they have reached no conclusions as to the means employed, the motive or the identity of those who might be responsible.

An early rumour had suggested Mr Litvinenko had possibly been responsible for his own death or had taken poison in order to implicate the Russian authorities.

Friends of Mr Litvinenko said last night they understood he was due to be buried as soon as today in a private Muslim ceremony in London.

However, other reports suggested the funeral could be delayed and take place later in the week.

Mr Litvinenko, who will be buried in a sealed coffin, converted to Islam shortly before his death and was given the Muslim equivalent of the last rites in hospital. Mr Litvinenko's father said his son converted to Islam shortly before his death on November 23.

"He told me of his decision two days before he died," Walter Litvinenko told Radio Free Europe.

"He said, 'Papa, I have to talk to you about something serious. I've become a Muslim'." He added that his son had made an "important personal decision" that would be respected.

Last night the Interfax news agency reported traces of polonium had been found at the British embassy in Moscow. Testing is thought to have been ordered after Andrei Lugovoi and Dmitri Kovtun, businessmen who met Mr Litvinenko before he was poisoned, met embassy officials.

Mr Lugovoi, a former KGB officer who now runs a juice factory, has said he will cooperate with Scotland Yard's inquiry. He is due to be interviewed today.

The Moscow prosecutor general's office said it was cooperating with officers from Scotland Yard despite "some departures from international standards" in the request for assistance.

British officers are only being allowed to sit in on interrogations by Russian prosecutors.

Mario Scaramella, an Italian academic and an associate of the dead man, who tested positive for polonium-210, left University College hospital in London yesterday and said he felt well.

Earlier, he said he had tried to warn Mr Litvinenko they were being targeted by "people linked with some clandestine organisations, not directly controlled by the Russian establishment but from Russia ... generally retired people from the security service".