FILE PHOTO - Former Russian tycoon Mikhail Khodorkovsky speaks during a Reuters Newsmaker event at Canary Wharf in London, Britain, November 26, 2015. REUTERS/Peter Nicholls

MOSCOW (Reuters) - Russian authorities have blocked a news website sponsored by Kremlin critic Mikhail Khodorkovsky less than a month before a presidential election, according to a block list available on the Russian communications regulator’s website.

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.

Polls show Putin is on course to be easily re-elected on March 18. Khodorkovsky, now based in London, frequently speaks out in public against Putin.

Roskomnadzor, Russia’s communications regulator, said on its website that the MBK media news site had been added to its block list on Tuesday at the request of the office of the General Prosecutor.

Khodorkovsky’s allies announced on Wednesday that the site had been blocked.

“We don’t know the reasons why we’ve been blocked. We haven’t received any letters from Roskomnadzor,” Veronika Kutsyllo, MBK’s chief editor, said in a statement.

Russia last year banned a pro-democracy movement founded by Khodorkovsky. It also blocked opposition leader Alexei Navalny’s website earlier this month, a move Navalny said was designed to blunt his campaign for a boycott of what he says is a sham vote.