Tax authorities have presented oil firm Slavneft, controlled by Gazprom and BP's Russian venture TNK-BP, with $10 million in back tax claims.

Slavneft was working "as usual" after police took documents related to purported tax evasion by a subsidiary in 2003, spokeswoman Maria Gridneva said Friday.

Slavneft is cooperating with the investigation into the Kalmykia-registered unit, which the producer bought after the year in question, Gridneva said, declining to elaborate.

An Interior Ministry source said a demand was brought against the unit for 2003, Vedomosti said Friday. The ministry was not available for comment.

Slavneft underwent regular international-standard audits and was regularly checked by tax authorities, the firm said. Previous audits and checks have produced no claims for 2003 through 2007, the firm said.

Gazprom became a shareholder of Slavneft in 2005, when it bought oil firm Sibneft, later renamed Gazprom Neft, from billionaire Roman Abramovich.

Therefore any tax claim, if confirmed by a court, would have no recourse to Gazprom but only to TNK-BP and Sibneft's former owners, who bought a majority in Slavneft at the end of 2002. TNK-BP declined to comment.

TNK-BP and Gazprom are also involved in talks over the giant Kovykta field, which Gazprom agreed to buy from TNK-BP last year.

Industry sources say Gazprom is eager to buy out TNK-BP's Russian shareholders completely.

Former Slavneft owner Mikhail Gutseriyev, who in 2003 headed Russneft, is currently wanted by Russian authorities on charges of tax evasion.

Reuters, Bloomberg, MT