A bank controlled by the owner of three British newspapers was raided by armed Russian masked police yesterday in a show of strength against one of Vladimir Putin’s most visible critics.

Alexander Lebedev, a Russian businessman who owns the London Evening Standard, Independent and Independent on Sunday, was inside the 11-storey building in Moscow when 50 officers swarmed in.

The billionaire was not arrested or questioned. However, agents from Russia’s FSB secret service and the interior ministry took away documents relating to a takeover of a financial institution by his National Reserve Bank.

Such raids – which are known as a ‘mask show’ – are commonly used by the authorities to fire a warning shot to critics of the Russian leadership, say liberals.

Mr Lebedev – a former KGB agent – is known for his outspoken criticism of the Kremlin and especially of Mr Putin, the prime minister, who is also a former KGB spy.

Two years ago, one of Mr Lebedev’s Moscow newspapers closed after it published a story claiming Mr Putin’s marriage was on the rocks and that he was involved in a romance with Olympic gymnast Alina Kabayeva, at 27 three decades his junior.

The story was denied, although rumours have persisted since then. Mr Lebedev denied any advance knowledge of the story and also subsequently denied it was correct.

However, he has spoken recently about how the original story surfaced in his newspaper.

Mr Lebedev is a key financial backer – alongside former Soviet leader Mikhail Gorbachev – of another investigative newspaper which is regularly critical of the Kremlin.

The businessman also has a long-running feud with ousted Moscow mayor Yuri Luzhkov and there was speculation last night that the raid could have been triggered by officers loyal to a man sacked last month by the Kremlin.

Mr Lebedev recently called for Britain to investigate Mr Luzhkov, who may seek asylum in London, for alleged corruption.

Mr Lebedev’s spokesman, Artyom Artyomov, said of yesterday’s raid: ‘I don’t see politics in this. It’s simply Russian idiocy.’

Police said the raid concerned an on-going criminal case.

They declined to give details but it is believed to be linked to the takeover of a bankrupt bank and the use of a large state loan paid to Mr Lebedev’s bank.

Mr Artyomov said law enforcement officers could have obtained any documents they needed without resorting to the extraordinary show of force.

Leading Kremlin foe Mikhail Khodorkovsky, once Russia’s wealthiest man, told a Moscow court yesterday he would die in jail if necessary, claiming that a likely new prison term amounted to a blatant political punishment.

The former chief of the Yukos Oil company, who has already been behind bars since 2003 on fraud charges, is now on trial accused of stealing £18billion worth of oil from his firm.