Russia's Economy Minister Alexei Ulyukayev has been detained in connection with an alleged bribe, BBC reported in the early hours of 15 November.
Russia's main anti-corruption body, the Investigative Committee (SK), said Mr Ulyukayev received a payment of $2m.
His ministry had given a positive assessment that led to the oil giant Rosneft acquiring a 50% stake in another oil company, Bashneft.
He is the highest-ranking Russian official to be detained since the 1991 coup attempt in what was then the USSR.
"This is about extortion of a bribe from Rosneft representatives accompanied by threats," Svetlana Petrenko, a spokesperson for the SK, told RIA Novosti news agency.
"Ulyukayev was caught red-handed as he received a bribe," she said.
The SK said the minister would soon be charged.
He could face a prison sentence of between eight and 15 years, if found guilty. Mr Ulyukayev was appointed economy minister in 2013; prior to that, he had been deputy chairman of Russia's central bank for a decade.
In October, Rosneft, an oil giant controlled by the Russian government, bought 50% of Bashneft for 330bn roubles ($5bn). Bashneft itself was one of Russia's largest state oil companies.