MOSCOW — Mikhail Prokhorov, one of Russia's richest tycoons and the owner of the New Jersey Nets basketball team, said Monday he will run against Prime Minister Vladimir Putin in March's presidential election.
Mr. Prokhorov, whose wealth Forbes magazine has estimated at $18 billion, has been cautious not to cross Mr. Putin's path in the past.
But the tycoon's candidacy may pose a serious challenge to Mr. Putin, whose authority has been dented by his party's poor showing in Russia's Dec. 4 parliamentary election and allegations of widespread fraud during the balloting.
Mr. Putin's party won about 50 percent of that vote, compared to 64 percent four years ago, and the fraud allegations have enabled opposition parties to mount massive anti-Putin protests in Russia.
"The society is waking up," Mr. Prokhorov said at the news conference in Moscow to announce his candidacy. "Those authorities who will fail to establish a dialogue with the society will have to go."
On Sunday, President Dmitry Medvedev promised on his Facebook page that the allegations of fraud during the parliamentary election will be investigated.
Mr. Putin's spokesman, Dmitry Peskov, predicted Monday that the probe will show that little vote fraud occurred and that it had no effect on the outcome.
"If you take all the cases of these alleged violations or whatever was published online, the total will be less than 1 percent of the overall number of votes," Mr. Peskov told the Associated Press.
Mr. Peskov's comment signaled that Mr. Putin who served as Russia's president from 2000 to 2008 and became prime minister only because of term limits is holding firm despite the protests, which have been the largest here since the 1991 collapse of the Soviet Union.
On Saturday, tens of thousands of people in Moscow and smaller numbers in more than 60 other cities protested election fraud and called for an end to Mr. Putin's rule.
Mr. Prokhorov, 46, said he hopes to win the support of Russia's growing middle class, which formed the core of Saturday's demonstrations.
However, he said he agrees with only some of the anti-Putin and anti-government slogans shouted out at the rallies. He did not say whether he plans to attend a follow-up protest in Moscow later this month.
He is one of several candidates who have said they will oppose Mr. Putin in the presidential election, including communist chief Gennady Zyuganov, who has finished second in past presidential elections.
Mr. Prokhorov's presidential bid follows his botched performance in the parliamentary race when he formed a liberal party under tacit support of the Kremlin, then abandoned the project under what he called Kremlin pressure.
He faces the immediate challenge of collecting the 2 million signatures required to qualify for the presidential race.
Several opposition candidates and parties in the past could not even run for parliamentary seats because their applications were turned down for technical reasons.