Russian President Vladimir Putin has dismissed a long-serving economy minister who was arrested on suspicion of taking a $2m bribe in a deal involving the state-controlled oil giant Rosneft.

Kremlin spokesman Dmitry Peskov told reporters on Tuesday that Putin fired Economic Development Minister Alexei Ulyukayev after losing trust in him.

The 60-year-old was arrested late on Monday after he allegedly received the huge bribe in a sting operation set by the FSB, the KGB's main successor agency, an investigative committee said in a statement.

Ulyukayev is the highest-ranking Russian official to be arrested while in office since the collapse of the Soviet Union in 1991.

Ulyukayev, who a Moscow court ruled should be put under house arrest for two months until January 15, faces up to 15 years in jail if found guilty.

The investigators said Ulyukayev took the bribe for giving the green light to Rosneft to take part in bidding for another oil company.

Who represents Russia?

Ulyukayev, who held the post since 2013 and worked in the government since 2000, told a Moscow court on Tuesday he was not guilty.

It was in his own interests to cooperate with the investigation as he valued his reputation, he said.

He is a known liberal figure who has spoken against an increasing government presence in the Russian economy.

Ulyukayev had opposed Rosneft's bidding for Bashneft, saying it was wrong for a state-owned company to take part in the privatisation drive. Putin defended the deal.

Peskov said the arrest had nothing to do with the Bashneft deal.

Putin was informed about the case when the investigation was first launched, Peskov told reporters.

"These are serious allegations," Peskov said. "Only a court can deliver a verdict."

'Nobody will believe'

Al Jazeera's Rory Challands, reporting from Moscow, said "almost nobody in Russia will believe this is purely about corruption, because this is a country where government ministers - supposed to be on fairly modest salaries - wear $40,000 watches, drive Bentleys, and live in mansions".

"Usually, when an arrest like this happens, it's something else going on - a power struggle possibly. One theory at the moment is [that] this is a power struggle that might involve the boss of Rosneft, [who is] a long-time ally of Vladimir Putin."

Russian Prime Minister Dmitry Medvedev appointed Deputy Economy Minister Yevgeny Yelin as acting economy minister after Ulyukayev's arrest.   

Source: Al Jazeera News And Agencies