Under an overcast London sky and in pouring rain, a former Russian spy was laid to rest yesterday to the sound of Islamic prayer.

The funeral of Alexander Litvinenko, known to friends as Sacha, brought together Christians, Muslims, Jews, and non-believers among the immigrants from Russia at Highgate Cemetery.

Within a stone’s throw of the old Soviet trade mission, once a nest of KGB spies, and the grave of Karl Marx, Litvinenko was laid to rest on a hill overlooking North London.

The historic cemetery now has the insubstantial grave of a former Russian spy, killed by radioactive poison, among its Victorian tombs.

Around 50 mourners were led up a colonnade-lined path to the graveside by Litvinenko’s widow, Marina, and his 12-year-old son, Anatoly.

Also there were his first wife, Natalia, and his son and daughter from his first marriage, Alexander and Sonia.

In barely audible Russian, his father Walter, told mourners gathered around the muddy grave: “Sacha was killed for telling the truth by those who are afraid of what he had to say. It was a cowardly murder by those who wanted to gag him in the most brutal way.”

But, as the coffin was lowered into the grave, the funeral was interrupted by an imam invited by one of Litvinenko’s friends, Akhmed Zakayev.

The preacher said Islamic prayers over the body of Alexander Litvinenko, according to what Mr. Zakayev says were the spy’s last wishes.

By contrast, Litvinenko’s wife, Marina, had wanted a non-denominational service at the grave. The split reflected a division over whether Litvinenko had converted to Islam the day before he died.

Mr. Zakayev told the DailyTelegraph last week that Litvinenko had converted and asked to be buried according to Islamic tradition.

Walter Litvinenko seemed to indicate that he believed Mr. Zakayev by attending Islamic prayers at Regent’s Park Mosque before the burial.

The family comes from the North Caucasus, near the war-torn region of Chechnya, where Muslim rebels are fighting Russian forces.

Litvinenko’s sister is married to a Muslim and one friend, Vladimir Bukovsky, said the family had visited mosques many times.

Mr. Bukovsky who, like Mr. Zakayev, helped carry the coffin, said: “It’s impossible to talk about conversion because there was no ceremony, but he felt deeply ashamed of Russia, and just before he died, he said he would like his remains to be buried in Chechen soil, which meant he agreed to going through a Muslim burial.”

Another close friend, who asked not to be named, said: “He was not a religious man. Akhmed calls him his brother and sincerely believes he converted to Islam. We are keeping an open mind. In the state he was, heavily sedated and on his deathbed, it is impossible to say. It was his last few days, and he was under a lot of influences, medical, mental, and emotional. What we can say is that he would often say, before he fell ill, ‘I’m Chechen’ or ‘I’m Muslim’ out of solidarity for a persecuted people and that the atrocities he saw in Chechnya were part of what provoked his break from the FSB.”