Russian opposition Alexei Navalny vowed Tuesday to make an ally of Russian President Vladimir Putin pay dearly for his Moscow poll win, saying he was preparing evidence to contest the vote results.
"We will do everything so that Sergei Sobyanin's victory will cost him dearer than any defeat," Navalny said.
"We now have documentary and legal evidence that the second round should have taken place and that the Moscow election commission falsified the poll," the 37-year-old said on popular radio Moscow Ekho.
Earlier Tuesday, the Moscow election commission upheld the final result of the Sunday vote showing incumbent mayor Sobyanin had received 51.3 percent of the vote, barely enough to avoid a run-off.
Navalny, who polled far more strongly than projected with over 27.2 percent, demands a partial vote recount, claiming the authorities allowed vote irregularities, particularly during at-home voting.
But in a sign the Moscow authorities were in no mood to hold a vote recount, the Moscow election commission upheld the final results earlier Tuesday.
Putin has been scheduled to attend the inauguration of the Moscow mayor on Thursday, a Kremlin source said last week.
A spokeswoman for the Moscow city hall said she was unaware when the inauguration might take place.
Some 10,000 Navalny supporters poured into a central Moscow square last night after the opposition leader beseeched them to turn up.
Speaking at the Bolotnaya Square, the focal point of huge anti-Putin protests that shook Moscow during winter 2011-2012, Navalny vowed to continue his fight for a political voice.
"We know how to turn our political machine which we created during this poll into a steamroller which will crush the United Russia," he said, referring to the ruling party.
He did not rule out that he might one day call for people to turn out for unsanctioned protests, "overturn cars and light smoke bombs."
"We will show that we are the main leading political opposition force in the country."
Analysts said Navalny's stronger-than-expected showing propelled him to celebrity status in Russian politics and made him a force to be reckoned with.
Navalny has been campaigning under the shadow of a five-year prison sentence on controversial fraud charges handed to him in July.
He was arrested in court but then suddenly released pending an appeal.
Analysts have said the Kremlin will now have to decide whether to send him back to jail or allow him to press along with his activism.