Russian police have questioned Alexander Lebedev, the former KGB agent, tycoon and newspaper owner, for more than three hours as part of a probe into alleged embezzlement at a bank that his business empire once controlled.

The questioning on Friday came after what Mr Lebedev claims was mounting pressure on his relatives and on his bank's employees following an armed raid on the bank in November by law enforcers as part of the same probe.

Mr Lebedev is a self-styled Kremlin critic who also owns the Russian opposition newspaper Novaya Gazeta and the UK newspapers the London Evening Standard and the Independent. He called on Vladimir Putin, the Russian prime minister, to intervene in the investigation, which he claimed was being propelled by a criminal gang working with senior officials in the federal security service and the interior ministry.

"I believe we are dealing with an organised mafia group which, using the cover of orders from above', is making bandit raids on my business," he said in an open letter to Mr Putin published on Friday.

"A colonel in the FSB came to me and spent a long time persuading me to leave the country: otherwise they would jail me," he said in the letter.

The police are investigating embezzlement from Rossiissky Kapital, a bank that Mr Lebedev's National Reserve Bank took over in autumn 2008. Mr Lebedev claims he uncovered that huge asset stripping took place at the bank before NRB took it over.

Mr Lebedev told the Financial Times following his questioning by police on Friday that arbitrary attacks on businesses by law enforcers were weighing hard on the investment climate.

"This is the climate we live in. Everyone is in this situation where the werewolves in epaulettes' in league with bandits have no limits on their power and they can go after whomever they like," he said, using an expression for corrupt law enforcers.

"These are the same people who went after [Yevgeny] Chichvarkin and [Sergei] Magnitsky," he said, referring to a Russian businessman who fled the country and lost his Evroset mobile distribution business after law enforcers accused him of kidnapping and extortion, and a lawyer who died in jail in 2010 after investigating corruption in law enforcement. "It is the same system."

Alexei Kudrin, the Russian finance minister, also on Friday criticised the government for failing to work by rules and instead deciding key questions regarding mergers and acquisitions depending on the closeness of private businessmen to officials in power.

The questioning of Mr Lebedev comes a day after police raided the Moscow offices of Yelena Baturina, Russia's richest woman and wife of the ousted Moscow mayor Yury Luzhkov, as part of a separate probe into alleged embezzlement. She has denied wrongdoing.