MOSCOW -- Black-uniformed special forces swept onto the airplane of Russia's wealthiest man Saturday and forced him back to Moscow, where he was ordered jailed on criminal charges -- a dramatic escalation of the politically charged probe into Russia's largest oil company.

Mikhail Khodorkovsky was charged Saturday with fraud, forgery and other crimes hours after the special forces troops, weapons drawn, surrounded his private plane at a Siberian airport.

The dramatic arrest alarmed the country's business and political elite, with many analysts saying the actions against Yukos are a Kremlin-directed campaign to keep Khodorkovsky out of politics.

Khodorkovsky, who has openly funded opposition parties, is the latest of Russia's super-rich oligarchs to be pursued by President Vladimir Putin's government. Tycoons Boris Berezovsky and Vladimir Gusinsky have gone into self-imposed exile to avoid criminal prosecution.

The Prosecutor General's office charged Khodorkovsky with fraud, forgery, embezzlement and personal and corporate tax evasion, the news agency Interfax reported. A spokesman for the office told The Associated Press that charges had been filed, but gave no specifics.

The charges were filed in Moscow, where Khodorkovsky was brought after he was detained during a business trip in Novosibirsk, the main city of Siberia.

Khodorkovsky could be kept until Dec. 30 in a pretrial detention facility, his attorney Anton Drel said. The shabby and overcrowded detention units are widely considered worse than Russia's prisons.

"The charges of the prosecutor are groundless. The detention of Mikhail Khodorkovsky is aimed at fanning a big scandal which would cover up the lack of evidence in the so-called Yukos case," Yukos spokesman Alexander Shadrin told AP.

Shadrin said Khodorkovsky's plane was surrounded by trucks after it landed in Novosibirsk and black-uniformed forces identifying themselves as FSB -- the main successor to the Soviet-era KGB -- boarded the plane shouting "put down your weapons or we'll shoot."

Worth $8 billion

The 40-year-old Khodorkovsky, whose wealth was estimated by Forbes magazine at $8 billion, is one of the most prominent of Russia's so-called "oligarchs" -- men who made huge, quick fortunes after the collapse of the Soviet Union by acquiring state property at low prices in deals whose ethics came under question.

The oligarchs are greatly resented by large numbers of Russians who did not benefit from the privatization of state property. Both parliamentary and presidential elections will be held in the coming months, and the standing of pro-Kremlin parties among ordinary Russians has been strengthened by the pressure being put on oligarchs by the authorities.

Under Putin, authorities stripped Gusinsky of his media empire and charged him with fraud and have charged Berezovsky with fraud in connection with an automobile company. Both now live overseas, where courts have rejected Russian extradition requests.

Both Gusinsky and Berezovsky allege that the actions against them are a political vendetta in retaliation for criticism of Putin. The Kremlin says that the prosecutor's office is an independent agency outside presidential control.

Khodorkovsky has given funding to the opposition Yabloko and Union of Right Forces parties and is believed to have personal political ambitions.

As head of the largest company dealing in Russia's largest export commodity, Khodorkovsky can wield substantial influence, and his potency was likely to increase with Yukos' recently finalized merger with Sibneft to create the world's fourth-largest oil exporting company.

On Thursday, investigators raided a public relations company that was doing work for Yabloko in the election campaign for the national parliament, reportedly looking for evidence connected to the Yukos probe.

Top Russian businessmen and political leaders across the political spectrum expressed concern about Khodorkovsky's detention, including Communist Party head Gennady Zyuganov, who told Interfax he was "extremely worried."

"We think that this extremely dangerous development of events can only be stopped by the clear, unambiguously presented position of Russian President Putin," said Anatoly Chubais, who oversaw the privatization of state assets in the 1990s and now heads the national electricity company.

Putin's failure to do this "will bring Russia into an irreversible process of worsening business conditions," he said.

The action may also raise a warning flag to foreign investors who have been increasingly putting money into Russia, boosting the economy strongly after the collapse of the ruble in 1998. Despite Russia's vast potential, many investors are leery of the country because of its capricious legal system and concerns about shareholder protection and corporate transparency.

Although U.S. companies have hesitated to step into the still-risky Russian oil market, Exxon Mobil was reported this month to be considering buying a 25-percent stake in the merged Yukos-Sibneft operation.

The investigation began in July with the arrest of Platon Lebedev, a top Yukos shareholder and board chairman of Menatep Group, on charges of theft of state property during the 1994 privatization of a fertilizer plant. Lebedev has remained in jail awaiting trial. Last week, prosecutors also filed tax evasion charges against a Yukos manager, Vasily Shakhnovsky, who oversees day-to-day company operations and is responsible for customer relations and auditing.