LONDON -- A former Russian banker shot and critically injured by an attacker as he returned to his east London apartment was under armed guard in a hospital Saturday, Sky News reported.

German Gorbuntsov was in a coma following the suspected assassination attempt Tuesday night as he entered a block of apartments close to the Canary Wharf financial hub.

The Russian newspaper Kommersant said the attacker "presumably" had a submachine gun and that Gorbuntsov was hit several times and hospitalized in critical condition.

But The (London) Times quoted a police spokesman as saying reports that a submachine gun was used were "speculative."

London's Metropolitan Police said it was "too early to speculate" on Russian reports the attack could be linked to the 2009 attempted murder in Moscow of another Russian banker, Alexander Antonov.

Gorbuntsov was a witness in that case, according to Kommersant. The newspaper said that Gorbuntsov, described as being in his 40s, was the former owner of several banks in Russia and Moldova.

Moldovan prosecutors opened an investigation into him after one of his banks, Universalbank, was closed, Komsomolskaya Pravda newspaper reported.

A German Gorbuntsov is listed on the website of Moldova's Center for Combating Economic Crimes and Corruption.

Anti-corruption prosecutor Viorel Radetchi told the Komsomolskaya Pravda, "We can write a thousand requests, but Britain will never extradite him to us."

But Kommersant wrote that he was a victim of a "raider attack" that saw him lose more than 70 percent of his stake in Universalbank, probably because of his affairs in Russia.

It added that the banker's lawyers believed the attack was connected to a 2009 assassination attempt on Gorbuntsov's business partner Alexander Antonov.

Lawyer Vadim Vedenin said Gorbuntsov had told him, "If I return to Russia, they will bury me."

His shooter, who ran from the scene, was described as being white, about six feet tall, thin and wearing dark clothing.