Moscow (CNN) -- Russian election authorities officially registered Prime Minister Vladimir Putin Monday as a candidate for president in next year's election, they announced on their website.





Putin will represent his United Russia party, the Central Election Commission said.





The move is the latest step toward Putin's reclaiming the presidency after switching to the prime minister's office because of a law barring him from serving more than two consecutive terms as president.





Russia's third-richest man, the billionaire New Jersey Nets owner Mikhail Prokhorov, announced this month that he will run against Putin for president.





Many ordinary Russians suspect the Kremlin put Prokhorov up to it to give the impression the contest is fair.





Last week, Putin brushed off widespread criticism that the December 4 parliamentary elections in Russia were falsified.





He said their results "reflect the actual line-up of forces in the country, as well as the fact that the ruling force -- the United Russia party -- has lost certain positions."





Tens of thousands turned out to protest the election results that returned Putin's United Russia party to power, but with a smaller majority.





Police estimated crowds in Moscow on December 10 at 25,000, while organizers said the total was 40,000, the state-run RIA Novosti news agency reported. Either figure would make the protests the largest in the Russian capital in 20 years.





Claiming the results of parliamentary elections were rigged, protesters chanted "Putin out."





They also braved freezing temperatures in other Russian cities to demonstrate against what they said was vote fraud.





Putin said in his question-and-answer session that protesters were positioning themselves for the presidential vote in March.





"It is obvious to me that the attacks on the latest election are secondary; their primary goal is the next election, the Russian presidential election," Putin said December 15.





The Organization for Security and Cooperation said in a preliminary report that some political parties had been prevented from running and the vote was "slanted in favor of the ruling party." Its election-observer mission detailed alleged attempts to stuff ballot boxes, manipulate voter lists and harass election monitors.





Secretary of State Hillary Clinton also said the United States had "serious concerns" about the election and called for a "full investigation" of apparent irregularities.
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