The spokesman for Lebedev, the owner of Britain's national Independent newspaper and London's Evening Standard, said the men had refused to provide their documents to bank employees.

Moscow police spokesman Viktor Biryukov said the people inside the building were "law enforcement officers, including investigators from the Russian Interior Ministry's main investigative department" who were carrying out checks in the bank "as part of a previously initiated criminal case."

He provided no details on those involved in the case or on the company that was being searched.

Earlier, the National Reserve Bank spokesman told RIA Novosti that police were seizing documents from the bank, in which Lebedev's National Reserve Corporation owns a 78-percent stake.

Police later said the search was connected to a criminal investigation into employees from another bank. But Lebedev, a billionaire who also co-owns the airline Aeroflot and the Russian opposition newspaper Novaya Gazeta, said in an interview that he believed it was organised in order to damage his interests. "I think it was some kind of rich, corrupted 'roof' that decided to carry it out," he said. The word 'roof' is used in Russian to mean the political or security muscle that protects an illegal business.

Speaking on Kommersant FM radio, Lebedev added: "Someone paid for [the raid on NRB] in the hope that clients would desert the bank." The businessman did not say who he believed to be the culprit and he was unavailable for comment today.

Rosnano spokesman Andrei Trapeznikov said the checks took place in "other organizations" located in the building and had nothing to do with the hi-tech corporation.

It was later disclosed that they were seeking evidence for a criminal investigation into Rossiyskiy Kapital, a bank which Lebedev's business bailed out during the financial crisis at the request of the government. Employees of Rossiysky Kapital are said to have transferred 450m roubles (£9m) to a shell company before NRB took charge.

In a Twitter post and a report on his blog, Lebedev criticised the nature of the raid, calling it a "masky show" and hinting that it might also have political roots. He called the policemen involved "loafers" who had ignored his earlier warnings that money had been embezzled from Rossiyskiy Kapital.

In a rare reproach to Russia's president Dmitry Medvedev, the tycoon added: "However much Medvedev is told 'don't frighten business', so far it's not working."

Police officer at the entrance to Lebedev's bank