Federal Security Service officers raided the Moscow office of British oil major BP on Tuesday, feeding market speculation that the state was hoping to hasten a deal that would see a state-run firm buy into TNK-BP, the company's main Russia venture.

The raid of BP's office on Novy Arbat, the second in as many months, came just two weeks after the inauguration of President Dmitry Medvedev, the former Gazprom chairman who has made legal reform an early goal of his rule.

"FSB investigators visited our offices to conduct an investigation," BP spokesman Vladimir Buyanov said, declining to provide details into reasons for the hours-long raid.

"The work of the office was not suspended, and we are cooperating with the investigation," he added.

The FSB press service refused to confirm or deny the raid. "We do not give out such information," a spokesman said.

Investigators were looking for documents related to Gazprom, Reuters reported, citing an unidentified source.

The latest move against BP fueled speculation that Gazprom was hoping to buy a majority stake in TNK-BP, a 50-50 joint venture between BP and a group of Russian oligarchs. The Russian shareholders ­ Mikhail Fridman and German Khan of Alfa Group, Viktor Vekselberg of Renova and Len Blavatnik of Access Industries ­ have denied that they are in talks to sell.

TNK-BP spokeswoman Marina Dracheva said the FSB had not raided the company's nearby offices Tuesday.

FSB officers first raided the offices of BP and TNK-BP in March, after arresting an Oxford-educated Russian-American employee at TNK-BP on charges of industrial espionage.

Soon after, the Natural Resources Ministry announced that it was conducting an investigation into TNK-BP's largest project, Samotlor. At the same time, 148 foreign BP employees contracted to work at TNK-BP were suspended amid problems getting their visas and work permits renewed.

The visa issue arose as the result of infighting among shareholders, who disagreed over the timing and pricing of a potential deal with Gazprom, sources have told The Moscow Times. The employees have since received their visas and permits through BP, but remain barred from working at TNK-BP.

A Tyumen court had been due Tuesday to hear a case brought against TNK-BP by a shady minority investor who claimed that the firm's use of BP employees was unfair to other shareholders. The hearing, brought by a firm called Tetlis, was postponed until Wednesday, news agencies reported.

Tetlis' web site links its founders to Alfa Bank, a subsidiary of Fridman and Khan's Alfa Group. Alfa Group issued a statement last week saying it had no connection to the firm.

The FSB raid on Tuesday could signal the state's desire to speed up a deal on Kovykta and TNK-BP ahead of Medvedev's visit to China on Friday, said Chris Weafer, chief strategist at UralSib.

TNK-BP agreed to sell Kovykta, a massive gas field in eastern Siberia, to Gazprom last summer for $700 million to $900 million. Finalization of the deal has been repeatedly delayed, and a late April deadline set by the two sides was not met.

"This is a potential embarrassment for Medvedev when he sits down with the Chinese," Weafer said. "Medvedev would much rather be able to go to Beijing at the end of this week with the Kovykta deal already done, because then he could say with credibility that this is where the gas is going to come from."

Moscow and Beijing, unable to agree on price, have long stalled on sealing any gas deals, despite Russia's construction of the large ESPO pipeline to China.

The unresolved TNK-BP issue could cast a shadow over the early presidency of Medvedev, who stepped down as chairman of Gazprom on the day of his inauguration May 7.

"The structure of TNK-BP is out of line with the new rules of strategic industries," said Weafer, referring to government policy that requires majority state control over the natural resources sector. "The state would rather see this restructuring be done sooner rather than later, that is, early in Medvedev's presidency."

Dracheva, the TNK-BP spokeswoman, denied a Reuters report that additional tax claims had been brought against the company.

"It's an old story. We have cleared all tax issues with respect to the period of 2002 to 2003," Dracheva said. "We have a tax audit signed by both parties, which shows the process is closed."

Reuters reported that the Interior Ministry was investigating claims against two TNK-BP units, Sidanco and Slavneft, which is half-owned by Gazprom, over unpaid taxes worth "several billion rubles."

The report said the claims refer to tax payments for 2002 and 2003 for Sidanco and 2003 for Slavneft. TNK-BP acknowledged in March that it was facing a 40 billion ruble ($1.7 billion) tax claim against Sidanco.