MOSCOW — Supporters of opposition leader Alexei Navalny rallied across Russia on Saturday, heeding his call to pressure authorities into letting him enter the presidential race with a wave of demonstrations on President Vladimir Putin’s 65th birthday.
The rallies came as Navalny himself is serving a 20-day jail term for calling for an earlier unsanctioned protest.
The rally in Moscow was markedly smaller than previous demonstrations in the Russian capital staged by Navalny this year but ended peacefully. A rally in Putin’s hometown of St. Petersburg attracted a bigger crowd and ended in clashes with police.
Several hundred protesters, most of them students, gathered on Moscow’s downtown Pushkinskaya Square, waving Russian flags and chanting ‘‘Russia will be free!’’ and ‘‘Let Navalny run!’’
Police warned them the rally wasn’t sanctioned and urged them to disperse, but let the protest continue for hours without trying to break it up.
Escorted by police, mostly teenage protesters later walked down Moscow’s Tverskaya Street toward the Kremlin, shouting ‘‘Putin, go away!’’ and ‘‘Future without Putin!’’
Police lines blocked them from approaching Red Square and they turned back. Several hours later, some demonstrators made a new attempt to march on the Kremlin, shouting ‘‘Putin thief!’’ Some briefly attempted to block traffic.
Police also didn’t intervene at first with a bigger unsanctioned rally in St. Petersburg, where over 1,000 gathered at Marsovo Pole park and then marched across the city, cutting off traffic and chanting ‘‘Russia without Putin!’’ and ‘‘Putin, retire!’’
Police later cracked down on the demonstrators, detaining dozens after some tried to break through police lines.
‘‘Putin has been in charge since I was born,’’ Dmitry Samokhin, 18, who was among protesters in St. Petersburg. ‘‘The country is mired in stagnation and I want to see changes.’’
The authorities’ decision to refrain from breaking up the Moscow protest, contrasted with a more forceful response to previous Moscow rallies called by Navalny, when police detained more than 1,000 demonstrators.
In St. Petersburg, police responded only after facing a violent attempt by protesters to break through their ranks.
Navalny’s headquarters called protests in 80 cities. Most were not sanctioned by authorities, but police largely refrained from breaking them up. The Siberian city of Yakutsk saw the toughest police response, where a few dozen demonstrators were reportedly detained.
Navalny has declared his intention to run for president in the March 2018 election, even though a criminal conviction that he calls politically motivated bars him from running. The 41-year-old anti-corruption crusader has organized waves of protests this year, casting a challenge to the Kremlin.
Putin hasn’t yet announced whether he would seek re-election, but he’s widely expected to run. With his current approval ratings topping 80 percent, he is set to win another six-year term in a race against torpid veterans of past election campaigns, like Communist Party chief Gennady Zyuganov.
Navalny argues that the high level of support for Putin comes from the lack of real political competition and urged supporters to help him get registered.
‘‘[Putin’s] 86 percent approval rating exists in a political vacuum,’’ he said. ‘‘It’s like asking a person who has been fed rutabaga his entire life how eatable they find it and the rating will be quite high. Listen, there are other things that are better than rutabaga.’’
The sarcastic analogy demonstrated Navalny’s stinging style, which has helped him get broad support among the young.
Navalny has worked to expand his reach with videos exposing official corruption and YouTube live broadcasts. His documentary about Putin ally Prime Minister Dmitry Medvedev and his alleged ill-gotten wealth has been viewed nearly 25 million times since its release in March, helping galvanize protests.
Heeding Navalny’s call, tens of thousands took to the streets in dozens of cities and towns across Russia in March and June, the biggest show of defiance since the 2011-2012 anti-government protests.
Unlike the past rallies, which were driven by anti-corruption slogans, Navalny this time focused on rallying support for his own presidential bid — a reason some gave for the smaller protest in Moscow.
‘‘Some people dislike Putin and the government, but that doesn’t mean they are willing to unequivocally back Navalny,’’ political analyst Valery Solovei said on Dozhd television.