Russian opposition politician Alexei Navalny vowed Tuesday that he would make an ally of Russian President Vladimir Putin pay dearly for beating him in Moscow polls, saying he was preparing to contest the results.
"We will do everything so that Sergei Sobyanin's victory will cost him dearer than any defeat," Navalny said after coming second to the Kremlin-backed incumbent in Sunday polls for Moscow mayor.
"We now have documentary and legal evidence that a second round should have taken place and that the Moscow election commission falsified the poll," the 37-year-old said on popular Moscow Ekho radio.
Earlier Tuesday, the Moscow election commission upheld the final result, saying that Sobyanin received 51.3 percent of ballots, just barely enough to avoid a run-off.
Navalny, who polled far more strongly than projected with over 27.2 percent, has demanded a partial vote recount, claiming the authorities allowed vote irregularities during at-home voting and at polling stations without observers.
In a blog post, Navalny said Sobyanin avoided a second round runoff with a margin of just 31,000 votes, accusing the winner of manipulations at the ballot box.
An anti-corruption blogger, Navalny shot to prominence during huge anti-Putin rallies in the winter of 2011-12.
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.
On Tuesday, he called on supporters to submit reports of violations and claimed he would have secured an outright victory if the voter turnout had reached 60 percent.
The turnout stood at a meagre 32 percent which apparently reflected Muscovites' apathy and lack of conviction that they can effect change.
But in a sign that the Moscow authorities were in no mood to hold a vote recount, the city's election commission upheld the final results on Tuesday.
Independent vote monitors have said irregularities were registered in Sunday's election, although they were not as serious as those witnessed in previous polls.
Widespread claims of wholesale fraud in 2011 parliamentary polls sparked unprecedented protests against Putin's ruling party and the Russian strongman himself.
Putin was scheduled to attend the Moscow mayor's inauguration on Thursday, a Kremlin source said last week.
Navalny said the authorities were in a hurry to hold the inauguration as soon as possible to cement Sobyanin's win.
"They understand perfectly well that we have thousands of observers from whom we need to collect papers in order to prepare thousands of complaints," he said.
Some 10,000 Navalny supporters poured into a central Moscow square Monday night after the opposition leader beseeched them to turn up.
Speaking at the Bolotnaya Square, the focal point of the 2011-12 anti-Putin protests, 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."
A Navalny representative, Nikolai Lyaskin, said on Tuesday that his supporters might hold another rally on Saturday, and that the authorities had already given their permission.
Navalny campaigned 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 was suddenly released a day later pending an appeal.
Analysts have said the Kremlin will now have to take the decision whether to send him back to jail or allow him to press ahead with his activism.