By Polina Devitt and Andrew Osborn
MOSCOW (Reuters) - Russia said on Wednesday it had banned a pro-democracy movement founded by Kremlin critic Mikhail Khodorkovsky which has called for big anti-government protests on Saturday ahead of a presidential election next year.
In a statement, the General Prosecutor's Office said it had decided that the activity of the Open Russia foundation, which it called a British organisation, was "undesirable" in Russia.
The ban comes days before what Open Russia hopes will be large anti-government protests it has called to try to put pressure on Putin, who is expected to run for what would be a fourth presidential term next year, to leave politics.
Khodorkovsky, a prominent Kremlin critic, said in a social media posting that prosecutors had acted because they were "touched to the quick" by the planned rallies.
The authorities regard any demonstrations not sanctioned in advance as illegal and were taken aback by the scale of large anti-corruption protests last month.
Along with Khodorkovsky's foundation, the Prosecutor's Office said it was also banning the Institute of Modern Russia, which it said was a U.S. organisation, and the Open Russia Civic Movement, which it said was British.
"These organisations are carrying out special programmes and projects on the territory of the Russian Federation aimed at discrediting the upcoming election results in Russia and having them declared illegitimate," it said.
"Their activity is aimed at inciting protest actions and destabilising the domestic political situation, which poses a threat to the foundations of the constitutional system and state security."
Under a 2015 law, organisations deemed "undesirable" can be banned and their members can be fined or jailed for up to six years for ignoring the ban.
Putin freed Khodorkovsky, once Russia's richest man, in 2013 after he had spent a decade in jail for fraud, a charge Khodorkovsky said had been fabricated to punish him for funding political opposition to Putin. The president has said he regards the businessman as a common thief.
"Russian authorities have worked relentlessly for many years to create the most hostile environment for civil society possible," Sergei Nikitin, the head of Amnesty International's Russian branch, said in a statement.
"Open Russia's activity was a huge obstacle for them, be it defending human rights, supporting independent candidates in elections at different levels, and acting as a media outlet. By banning this organisation, they think they've overcome this obstacle."
(Editing by Andrew Roche)