MOSCOW — Russian opposition leader Alexei Navalny demanded a recount Monday in Moscow’s mayoral election after official results showed that the Kremlin-backed incumbent barely escaped facing him in a runoff.
Russia’s most respected monitoring group also questioned the accuracy of the vote.
The Moscow Election Commission said Monday that former Kremlin chief of staff Sergei Sobyanin won just over 51 percent of the vote while Navalny garnered 27 percent in second place, a strong result for a Russian opposition leader.
If Sobyanin, 55, had won less than 50 percent, he would have faced a runoff with the charismatic 37-year-old Navalny, who has risen to wide prominence in the past few years with his anticorruption campaign.
‘‘We do not recognize these elections,’’ Navalny told reporters. ‘‘Sobyanin can’t consider himself the mayor of all Muscovites, he can’t consider himself a lawfully elected mayor unless he agrees to our demands and allows a recount of the vote.’’
Leonid Volkov, chief of Navalny’s election campaign, said the key violation they are contesting is the voting-from-home totals, in which the vote count showed what he called an abnormally high number of votes for Sobyanin. Those votes are from people considered too infirm to get to polling stations.
On Monday night, Navalny sought to defuse anger over the results, telling a crowded square of cheering supporters to celebrate his surprisingly strong finish as a victory that gave rise to real political competition in Russia.
Navalny has claimed that Sunday’s vote was manipulated to give Sobyanin the slim majority he needed to win in the first round and avoid a runoff.
But rather than call for angry street protests like those he led after the fraud-tainted 2011 national parliamentary election, Navalny urged his supporters to keep up the kind of grass-roots political activism that helped him defy all expectations and win 27 percent of the vote.
Sunday’s election was in some ways less about Sobyanin, who many agree has brought positive change to Moscow since taking over three years ago, and more about the depth of discontent in the Russian capital with President Vladimir Putin’s rule, especially among the young and middle class.
Navalny, 37, attracted thousands of enthusiastic volunteers to help him take his campaign to the streets of Moscow.
‘‘During these elections, politics in Russia was finally born,’’ Navalny told the crowd that filled Bolotnaya Square.
The Navalny who took the stage Monday night was a more restrained and mature-sounding version of the fiery protest leader who inspired the mass protests against Putin that stretched through the winter of 2012, some of them held on the same square across the river from the Kremlin.
He said the time may come when he will call on his supporters to protest in defiance of police, ‘‘to turn over cars and light flares, whatever else,’’ but for now he asked them to keep up their political work through elections.
Monday’s rally largely answered the question of how Navalny planned to respond to the election results. The next question is whether the Kremlin remains determined to see him in prison after he won the votes of 630,000 Muscovites.
Navalny was convicted in July of embezzlement in a case seen as part of a Kremlin effort to sideline him, but his strong showing at the polls could lead to a reduction in his five-year sentence, if the Kremlin feels this would help settle discontent.
Nikolai Petrov, a scholar who studies Russian politics, said jailing Navalny now would be sure to trigger huge protests. ‘‘I would not expect the Kremlin to do this stupid mistake, although I cannot exclude such’’ a possibility,’’ Petrov said during a telephone briefing organized by the Wilson Center in Washington.
Golos, Russia’s leading independent election monitor, said the voting Sunday appeared to have gone smoothly, but it pointed to violations that could have tipped the balance in favor of Sobyanin. ‘‘Everyone has doubts,’’ Golos executive director Grigory Melkonyants said. ‘‘This is not a convincing victory.’’
Sobyanin, however, told his supporters late Sunday that they should be proud. ‘‘We organized the fairest, most competitive and most open elections in the history of Moscow,’’ he said.
This mayoral election was the first in Moscow since 2003 and included six candidates. Last year, the Kremlin reversed Putin’s 2004 decree abolishing direct elections for Moscow’s mayor and other regional leaders.