Police detained more than 100 supporters of jailed opposition leader Alexei Navalny on Saturday as thousands rallied nationwide on President Vladimir Putin's 65th birthday, calling for the leader to retire. Mr Putin, who has now reached the official retirement age of lower-ranking state employees, is widely expected to run again in next year's presidential election and enjoys a high approval rating. Mr Navalny has declared his intention to run in the election next March and was campaigning in provincial cities as part of his long-shot bid for the presidency. He was arrested late last month and a court last week sentenced him to 20 days in jail on charges of repeatedly violating a law on organising public meetings. Demonstrators attend an unauthorised anti-Kremlin rally called by opposition leader Alexei Navalny Credit: AFP Mr Navalny's arrest galvanised supporters in 80 cities, who turned out on Saturday in a nationwide protest against the ruling. "I came out to support the opposition because I don't agree with the course our country has taken," said Anatoly Morozov, a student dressed in a fox costume at the St Petersburg protest. "The ignorance and insanity has reached impossible levels." Protesters chanted "Free Navalny," "Putin's a theif" and "Fourth term in prison," referring to the president's expected run for re-election. Last year Mr Putin played hockey on his birthday, but the mood this year was not as light. The Kremlin said on Friday he would be taking phone calls and attending a meeting of the security council in Sochi. Russian riot-police seen blocking Liteiny Prospekt on today Navalny support march in St-Petersburg Credit: DMITRI BELIAKOV for The Telegraph Local authorities refused permission for many of the demonstrations and told residents not to attend. Mr Putin's spokesman warned that violators could be prosecuted, but activists declared they would go ahead anyway. “Many supporters want to see Navalny as president, they come out on the streets because for now that's the only format in which they can express this,” said Polina Kostyleva, the head of Mr Navalny's St Petersburg campaign office. She was detained and fined this week after police raided the office and found fliers about the protest. A demonstrator chats slogans during an unauthorised anti-Kremlin rally Credit: AFP Police in several cities detained campaign activists before the protests even began. In the Urals city of Yekaterinburg, where an estimated 700 people came to the demonstration including maverick mayor Yevgeny Roizman, police detained at least 18 people, according to independent monitoring group OVD-Info. In Moscow, protesters chanted “down with the tsar” and marched toward the Kremlin before running into a wall of riot police. Russian riot-police seen arresting protester on today Navalny support march in St-Petersburg Credit: DMITRI BELIAKOV for The Telegraph At least one protester was detained, but there were no mass arrests that took place at protests in June, when 850 people were taken into custody. Police said 700 people had participated while activists put the number as high as 2,000.