Thousands of Russian demonstrators converged on central Moscow Saturday, protesting President-elect Vladimir Putin's third term in office amid allegations of election fraud.

The demonstrators are challenging the authority of Mr. Putin, who won 64 percent of the vote in Sunday's election. He served as president from 2000-2008, but term limits prevented him from running for a third consecutive term. He then became prime minister – a position he currently holds.

Mr. Putin's ruling United Russia party won 238 of the 450 seats in the December parliamentary election. Allegations of fraud in the election sparked mass protests, led by the opposition.

Tens of thousands of people took to the streets in Moscow and elsewhere demanding a rerun of the elections in the largest demonstrations in post-Soviet Russia.