Ex-Russian spy Alexander Litvinenko, who died last month after being poisoned, was to be buried Thursday at the Regent's Park Mosque in London, confirmed FOX News.

Around 30 family members and friends have traveled to Britain from Russia and Italy to attend the ceremony in north London, according to a family friend who spoke on condition of anonymity because he was not authorized to release details about the service.

British police on Wednesday upgraded their inquiry, saying they were treating the death of Litvinenko as murder — rather than as a suspicious death.

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Officers continued inquiries in Moscow, where they are seeking to question several men but are facing resistance from Russian authorities.

Litvinenko's friend Alexander Goldfarb said Thursday he could not confirm the date of the funeral in advance, but insisted it would be a nonreligious ceremony.

"There has been suggestion that he had converted to Islam before his death; that is completely wrong — he was not a religious man. His wife has insisted that the funeral is nondenominational," Goldfarb told The Associated Press.

Litvinenko, who died Nov. 23 after being poisoned with the rare radioactive element polonium-210, was to be buried in a sealed coffin, Goldfarb said.

Mario Scaramella — the security expert who met Litvinenko on Nov. 1, the day Litvinenko fell ill — was in good health after being discharged from the hospital Wednesday, University College Hospital spokesman Ian Lloyd said. Scaramella was admitted to the hospital after also testing positive for polonium-210.

The Associated Press contributed to this report.