MOSCOW (AP) _ Russian prosecutors said Wednesday they are investigating the possible role of a former owner of the Yukos oil company in the radiation poisoning death of one-time Russian intelligence agent Alexander Litvinenko.

They did not explain the basis for the allegations against Leonid Nevzlin, who now lives in exile in Israel.

Russia has unsuccessfully pressed for the extradition of a number of Kremlin critics in recent years, including Nevzlin and tycoon Boris Berezovsky, who lives in Britain.

Amir Dan, a spokesman for Nevzlin, dismissed the prosecutors' allegations.

``We all know the ways of the KGB and the Russian government, and these claims are ridiculous and are not worthy of comment,'' he told The Associated Press.

Alex Goldfarb, a friend of Litvinenko's active in London's community of Russian expatriates and Kremlin critics, called the charges against Nevzlin a ``clumsy effort'' by Moscow to shift blame from itself.

``This is sheer nonsense,'' he told the AP. ``Everybody knows that all evidence points to Russia. The way the Russian government, the Russian prosecutors are handling it is only adding to that suspicion that it is the Russian government behind this.''

Litvinenko died in London on Nov. 23 after he was exposed to a rare radioactive element, polonium-210. In a deathbed statement, he accused President Vladimir Putin of ordering his murder, allegations which the Kremlin has dismissed.

Nevzlin fled Russia after authorities launched a criminal investigation against Yukos, once Russia's top oil producer, in 2003.

Nevzlin told the AP last month that Litvinenko had given him a document related to Yukos. He said he believed the poisoning death was tied to Litvinenko's investigations of the Russian government's dismantling of the company.

On Wednesday, the Prosecutor General's office said Nevzlin and other Yukos figures wanted by Russia could have ordered Litvinenko's killing as well as the poisoning of another former agent, Dmitry Kovtun.

``We are checking the possibility that these crimes could have been ordered and organized by the same group of people who are wanted internationally, one of whom is Leonid Nevzlin,'' prosecutor's spokeswoman Marina Gridneva said on state television.

The statement said prosecutors had formed a special investigative unit and were preparing to file international requests for assistance in the case and possible extradition demands.

Britain sent Scotland Yard detectives to Moscow this month to interview witnesses but they were allowed only to sit in on questioning by Russian prosecutors.

Russia also launched its own investigation, seen as a bid to keep control of the politically explosive case, which has threatened to drive relations between Britain and Russia to post-Cold War lows.

Meanwhile, Russian authorities on Wednesday questioned the imprisoned Mikhail Khodorkovsky, the former chief executive of Yukos oil, as a suspect in a new criminal inquiry, his lawyer said.

Yuri Schmidt said Khodorkovsky was questioned on suspicion of involvement in money-laundering _ allegations the lawyer dismissed as politically motivated.

Khodorkovsky, once Russia's richest man, is currently serving an eight-year sentence on fraud and tax evasion charges in a prison in eastern Siberia.

``The new case is a continuation of selective justice aimed at applying moral and physical pressure on Mikhail Khodorkovsky, further destruction of Yukos and the confiscation of assets,'' said Yuri Schmidt, Khodorkovsky's lawyer, in a statement posted on a Web site for the tycoon's supporters.

Nevzlin, who according to Forbes magazine had a net worth of about $2 billion before Yukos' collapse, has been charged by Russia with ordering the 2002 murder of a married couple.

A former Yukos security officer has been jailed since mid-2003 in the case, which was allegedly business-related.

Litvinenko fell ill after meeting with Russian businessman Kovtun, Andrei Lugovoi, also an ex-Soviet agent, and Vyacheslav Sokolenko, head of a private Russian security firm, at a bar at the Millennium Hotel in London.

All three men have denied involvement in the former spy's death. Kovtun himself has been contaminated with radiation and is undergoing treatment at a Moscow hospital.

The unexplained murder has inspired widespread speculation about who may have been behind it.

Many Western analysts suspect the Kremlin, though there is no evidence that the Russian government was involved.

Pro-Kremlin lawmakers have suggested _ also without offering evidence _ that Berezovsky was responsible, as part of a plan to blacken the reputation of Putin and the Kremlin.

Mario Scaramella, an Italian who also met with Litvinenko the day he fell ill, is seeking release from prison, his lawyer said Wednesday. His arrest is not believed to be directly connected to Litvinenko's murder.

Scaramella was questioned for about six hours by Italian prosecutors in a Rome jail, where he is being detained.

His lawyer, Sergio Rastrelli, said his client is accused of slander. Scaramella's father and Italian news reports say the suspect was accused of international arms trafficking.

``We intend to seek his immediate release from prison,'' Rastrelli told reporters. ``My client will respond to all questions and will clarify any ... misunderstanding.''