Matt Dunham, Associated Press
Marina Litvinenko, the widow of former Russian intelligence officer Alexander Litvinenko, arrives with her son Anatoly on the day she is due to give evidence at the inquiry into her husband's death at the Royal Courts of Justice in London, Monday, Feb. 2, 2015. The body of former Russian agent Alexander Litvinenko was so radioactive that his post-mortem was "one of the most dangerous" ever undertaken and the isotope that killed him so rare it would not have been discovered by a normal autopsy, a pathologist said Wednesday.

LONDON — Alexander Litvinenko couldn't have poisoned himself accidentally with radioactive polonium, and received threats for years before his death, the former Russian spy's widow said Tuesday.

Marina Litvinenko told an inquiry that her husband couldn't have acquired nuclear materials because it was illegal and he would "not do any illegal things in this country."

A former Russian security services agent who moved to London and became a strong critic of the Kremlin, Litvinenko became sick after drinking tea laced with polonium-210 at a London hotel on Nov. 1, 2006.

He died on Nov. 23, a day after signing a statement blaming Russian President Vladimir Putin for his poisoning. His wife said his last words to her were "I love you so much.'"

She said Litvinenko, who had become a supporter of the Chechen cause, converted to Islam from his hospital bed. She said that when he told his Russian Orthodox father about the conversion, the older man said: "At least you're not a communist."

Marina Litvinenko said her husband had received threats after he began speaking out against the Kremlin.

In 2002, he received an email from a former colleague saying "get your will ready in advance." The couple's London home was later fire-bombed.

Two weeks before he was poisoned, Litvinenko appeared at a public meeting in London and blamed Putin for the murder of journalist Anna Politkovskaya, who had been shot dead in Moscow.

British police have named two Russian men, former KGB agent Andrei Lugovoi and Dmitry Kovtun, as prime suspects in Litvinenko's death. They deny involvement, and Russia has refused to extradite them.

An inquiry led by judge Robert Owen is examining the circumstances of Litvinenko's death and whether the Russian state was involved.