Dudley has been at the center of a conflict between the British oil major and a consortium of four Russian billionaire shareholders, each having 50% in Russia's third largest oil producer. The Russian investors have accused him of acting only in BP's interests and demanded his dismissal.
"We cannot impede Robert Dudley's work... A work permit... has been issued," the Ekho Moskvy radio quoted migration service spokesman Konstantin Poltoranin as saying on Monday.
Earlier on Monday, however, Poltoranin said Dudley's 10-day visa extension would not allow him to work in Russia. He said the executive would be issued a new visa as soon as he submitted the necessary documents.
Dudley's visa expired on July 19, but the migration service issued a transit visa for him, which is valid until July 29. Dudley needs to provide a valid employment contract to have his visa renewed.
The Russian shareholders in the company said last week that the contract had expired late last year and had not been officially renewed.
BP argues that the contract is valid, saying that it has not been formally terminated and has therefore been extended automatically in line with Russian law.
The Russian investors have criticized the BP-appointed U.S. executive for his strategy and management of TNK-BP. BP said they want to seize control of the company. The dispute has been followed closely by foreign investors.