Russian Prime Minister Vladimir Putin scored an apparently decisive victory in Sunday's presidential election to reclaim the Kremlin post he occupied from 2000 to 2008.

At a late-night appearance before tens of thousands of his supporters outside the Kremlin, a tearful Mr. Putin thanked his supporters for helping him “prevent the country falling into the hands of enemies trying to usurp power.” He said he had won an “open and honest struggle.”

Opposition leaders decried the election as a sham and said they were planning mass protests for Monday in Moscow and Russia's other big cities. But Mr. Putin remained triumphant, telling the crowd “I have promised you we would win and we have won! Glory to Russia.”

Exit polls and partial results suggest that Mr. Putin will win about 59 percent of the vote — more than enough to avoid a second-round runoff. His nearest rival, Communist Party head Gennady Zyuganov, is a distant second with about 17 percent, while nationalist Vladimir Zhirinovsky, billionaire Mikhail Prokhorov and Putin's former ally Sergei Mironov are in single digits.

Complete results are expected Monday.

Three policemen were killed in an attack on a polling station in Russia's troubled Caucasus republic of Dagestan Sunday. A local official said the men were killed as a result of a gunfight with the assailants hours after the polling station closed.

The election was marred by accusations of widespread violations. Independent watchdog agency Golos says it has registered more than 3,000 reports of irregularities, including so-called “carousel voting,” a practice in which busloads of voters are taken from one polling place to another to cast ballots.

A spokesman for Golos told VOA that if the elections had been clean, Mr. Putin would have had to face a second round. He said the volume of fraud complaints was as high as in the parliamentary elections in December.

Communist Party candidate Zyuganov denounced the elections as “illegitimate, unfair and not transparent.” Prokhorov also criticized the vote, saying “I deliberately agreed to play by someone else's rules.” Others complained of doctored voting lists and said pro-Kremlin business leaders installed voting booths in factories, pressuring workers to vote for Mr. Putin.

Mikhail Gorbachev, the last Soviet leader, told the Interfax news agency that he doubts the results reflect the true will of Russians. He said the challenge now is to change the country's election system to make voting fair, and to restore direct election for governors.