Russia raised pressure on BP's joint venture on Tuesday as the Interior Ministry said it was probing a big tax evasion case while TNK-BP itself said it is struggling to renew visas for almost 150 employees from BP.
The news follows last week's raids of TNK-BP, half owned by BP and half by a group of Russian billionaires, and the arrest of an employee for suspected industrial espionage.
Analysts have given conflicting views about the reasons of the crackdown, with theories ranging from the Kremlin putting pressure on the Russian owners to sell out, to infighting between different Kremlin clans, or a renewed dispute between the Russian and British shareholders within the firm itself.
The pressure comes as ties between London and Moscow hit their lowest point since the Cold War, although President-elect Dmitry Medvedev again denied any political motivation behind the events around Russia's No. 3 oil firm.
The Interior Ministry said on Tuesday it was investigating tax evasion worth over $40 million involving Sidanco, an oil unit which TNK-BP liquidated in 2005 after merging it with other assets during a consolidation.
"The investigative department of the ministry has opened a criminal investigation against Sidanco according to the article 199 of the Criminal Code, part 2 -- large-scale tax evasion," said Angela Kastuyeva, spokeswoman for the department.
She said the sum involved was over 1 billion roubles ($42.2 million).
Last week the ministry gave conflicting reasons for the searches, saying they were related to a criminal investigation of a false bankruptcy of Sidanco in 1999. It later said searches were related to a case against TNK-BP managers.
Tuesday's comments were the first mention by the ministry of tax evasion, although it added the case was opened in mid-2007.
TNK-BP's other unit, Slavneft, which is co-owned by state gas firm Gazprom, is facing a separate tax evasion probe.
TNK-BP, which has faced but settled a number of tax evasion claims in recent years, declined immediate comment on the new claim. But it said it was struggling to renew visas for 148 people working on secondment from BP since January due to legal changes.
"We are confirming that 148 secondees of BP have been recalled from TNK-BP because their legal status has yet to be brought in line with Russia's migration legislation," said a TNK-BP spokesman, confirming an earlier report by Reuters.
The secondees, mainly British and U.S. engineers, will stay in Russia but move to the much smaller BP office. If the visa situation is normalized, they will return to TNK-BP.
TNK-BP also employs 40 former BP executives, such as CEO Robert Dudley, who are unaffected by the visa problems.
TNK-BP's illiquid stock did not move on Tuesday.
BP relies on TNK-BP for a quarter of its output but negative news has not weighed on BP shares in the past week. On Tuesday, it traded up 3.5 percent, outperforming a 2.5 percent rise in the DJ European oil and gas sector index.
"At this stage I wouldn't worry too much but you can't be sure it is not linked to something bigger," said Paul Mumford, senior fund manager at Cavendish Asset Management, which has 660 million pounds under management and owns BP stock.
The Kremlin has been consolidating its presence in the oil sector. There has been market speculation that state corporations were eyeing TNK-BP, one of the biggest foreign investments in Russia which in 2006 had profit of $6.6 billion.
Moscow and London also have rocky diplomatic relations due to a row over Russia's refusal to extradite a former KGB agent wanted for trial in Britain over the murder of a Kremlin critic in London.
That dispute led to diplomats being expelled from both countries and to the forced closure of two regional offices of the British Council.