MOSCOW, Dec. 20 -- Russian President Vladimir Putin on Friday pardoned Mikhail Khodorkovsky, a former oil tycoon and one of Russia's most famous prisoners, in a move that experts say will allay investors' fears to do business in the country.

"Guided by the principle of humanism, I order to grant pardon to Mikhail Khodorkovsky, freeing him from further imprisonment," Putin said in a presidential decree, which took effect immediately.

Foreign investors will welcome the pardon, though roots of unfavorable business climate in Russia are much deeper than the fate of a particular businessman, said Konstantin Simonov, director general of the Moscow-based National Energy Security Foundation.

"If this is the first step to reverse allegedly unjust courts' rulings and outlaw corporate raiding, it could pave the way for stronger capital inflow to Russia," he told Xinhua.

Meanwhile, he acknowledged that Khodorkovsky's imprisonment has never scared investors out of the country.

Alexei Linetsky, head of the Board of Directors of the Moscow Judicial Agency, said by pardoning Khodorkovsky, Putin eliminated speculations that the tycoon had been his personal foe.

Khodorkovsky, once a co-owner of the Yukos oil company and one of the seven richest men in Russia, was arrested in 2003 onboard a plane while on a business trip.

In May 2005, a Moscow district court sentenced him to nine years in prison for fraud and tax evasion. In 2012, the Russian Supreme Court revised his prison term to expire in August 2014

"He has spent more than 10 years in jail and that's a serious term," Putin said Thursday after he concluded a four-hour annual press conference in Moscow, adding that Khodorkovsky had written a pardon petition.

"Putin, an experienced politician, definitely has calculated what the public reaction to his decree could be. And he skillfully selected the timing to announce his decision," Linetsky said.

According to Linetsky, Putin's pardon does not mean Khodorkovsky has become immune from future prosecution.

"In line with the Russian law, for 10 years from now on, Khodorkovsky will be regarded as a person with a criminal record and be restricted in certain rights," he said.

The expert believes that Putin had made the decision quite long ago but was waiting for a right moment. That moment came as the State Duma, lower house of parliament, announced amnesty to some 25,000 people this month to mark the 20th anniversary of the Russian Constitution.

Whatever the future of Khodorkovsky would be, Putin has made one more step to improve the country's image even in the eyes of his opponents, said the experts.