Moscow, Oct 3: Opposition leader Alexei Navalny was sentenced here on Monday to 20 days in jail for organising unauthorized protests against the government of Russian President Vladimir Putin. Navalny, who has already spent 40 days behind bars this year after two previous convictions related to demonstrations in Moscow, was detained last Friday as he was preparing to travel to Nizhny Novgorod for an unauthorized rally, Efe reports. This latest sentence means that the would-be 2018 presidential candidate will not be able to take part in a mobilization planned for next Saturday in Putin's native St. Petersburg to coincide with the president's 65th birthday. Russian electoral authorities say Navalny can't run for office because he is serving a suspended sentence for fraud pursuant to a December 2016 conviction that the anti-corruption activist vows to appeal. Navalny, 41, said in court that he is being persecuted for political reasons. In recent months, municipal governments in various important Russian cities, including Samara, Ufa and Krasnoyarsk, have denied requests from Navalny to hold public events. The Council of Europe has called on the Russian government to allow Navalny to stand in the 2018 presidential election, where Putin is expected to seek another six-year term. A poll conducted in April by the Levada Center found that 18 percent of Russians would vote for Navalny for president.