Russia is refusing to provide witnesses or information to the independent investigation into alleged corruption in the multibillion-dollar U.N. Oil-for-Food program (search) in Iraq, an official close to the investigation said Wednesday.

The official, speaking on condition of anonymity, said Russian diplomats "dug in their heels" during a meeting in Moscow this week with members of the independent inquiry.

Russia is a veto-wielding member of the U.N. Security Council which approved Secretary-General Kofi Annan's (search) recommendation in April to set up an independent panel headed by former U.S. Federal Reserve Chairman Paul Volcker (search) to probe all aspects of the Oil-for-Food program, including actions of U.N. member states.

Under the program, Russian companies were major recipients of contracts from Saddam Hussein's government for the sale of Iraqi oil and the supply of humanitarian goods to Iraq.

Launched in December 1996 to help Iraqis cope with U.N. sanctions imposed after Saddam's 1990 invasion of Kuwait, the program allowed the former Iraqi regime to sell unlimited quantities of oil provided the money went primarily to buy humanitarian goods and pay reparations to victims of the 1991 Gulf War. Saddam's government decided on the goods it wanted, who should provide them, and who could buy Iraqi oil — but the U.N. committee overseeing sanctions monitored the contracts.

Russia's Foreign Ministry said in a statement earlier Wednesday that Russian exporters operating under the program did not violate sanctions.

"In particular, it was noted that during the humanitarian operation in Iraq, Russian exporters strictly adhered to the sanctions regime," the ministry said in a statement.

The resolution supporting Volcker's investigation called on the U.S.-led coalition in Iraq, the Iraqis themselves, and all 191 U.N. member states and their regulatory authorities "to cooperate fully by all appropriate means with the inquiry."

Russia had initially opposed Volcker's request for a Security Council resolution on grounds that a council statement was enough and its members should not look backward and "stir up the old issue" of Oil-for-Food. But it relented and supported the resolution.

The official close to the Volcker inquiry said, however, that "the Russians have been reluctant to provide witnesses and information."

"They are being problematic and they are digging in their heels. They're not handing over materials," the official said.

A report by top U.S. arms inspector Charles Duelfer (search), released last month, alleged that Saddam issued secret vouchers for purchase of oil to an array of officials and political figures from various countries, dominated by Russia, France and China. That oil could then be resold at a profit.

Saddam allegedly issued the vouchers with the aim of currying favor among U.N. Security Council members.

U.S. Congressional investigators on Monday estimated that Saddam had raised more than $21.3 billion in illegal revenue, using the Oil-for-Food program and other schemes, like the illegal smuggling of oil.

In Russia, the recipients allegedly included the presidential administration's office, top oil companies Yukos and Lukoil, and ultranationalist lawmaker Vladimir Zhirinovsky, the report said.

At a news conference last month, Volcker said his investigators had received good cooperation from the U.S. and Iraqi governments, and a promise of cooperation from France.

But he said there had been "a little resistance here and there," citing the French bank BNP Paribas, where the Oil-for-Food program had its account, and the American accounting firm Ernst & Young which was hired by the Iraqi Board of Supreme Audit to review more than 20,000 files from Saddam's regime related to the Oil-for-Food program.