(CBS/AP) MOSCOW - Vladimir Putin has claimed victory in Russia's presidential election, which the opposition and independent observers say has been marred by widespread violations.
Putin made the claim at a rally of tens of thousands of his supporters just outside the Kremlin, thanking his supporters for helping foil foreign plots aimed to weaken the country.
Putin tallied 58-59 percent of Sunday's vote, according to exit polls cited by state television.
Communist Party candidate Gennady Zyuganov received about 18 percent, according to the survey, and the others nationalist Vladimir Zhirinovsky, socialist Sergei Mironov and billionaire Mikhail Prokhorov were in single digits.
With just over 20 percent of all precincts counted, Putin was leading the field with 63 percent of the vote, the Central Election Commission said.
Putin, president from 2000 to 2008, was expected to easily win the Sunday election against four challengers. But if credible evidence of vote manipulation emerges, it would bolster the determination of opposition forces to continue the unprecedented wave of protests that arose in December.
The independent elections watchdog agency Golos said it was receiving reports of so-called "carousel voting," in which busloads of voters are driven around to cast ballots multiple times.
"There have been many people voting more than once, driven around in buses in large numbers" in Moscow, said Golos head Lilia Shibanova, who said similar reports had been received from Novosibirsk, Russia's third-largest city, and the city of Barnaul in southern Siberia.
"We, of course, expected carousels, but not on this scale," Alexei Navalny, one of the opposition's most charismatic leaders, said on Twitter.
Allegations of widespread vote fraud in parliamentary elections set off the massive protests against Putin, who has remained Russia's paramount leader despite stepping down from president to prime minister four years ago due to term limits. They were the largest public show of anger in post-Soviet Russia and demonstrated growing frustration with corruption and political ossification under Putin, who as prime minister has remained Russia's dominant politician.
Golos' website recorded well more than 1,000 complaints of irregularities, including voter lists of questionable validity and nonfunctioning cameras in voting stations.
Web cameras were installed in Russia's more than 90,000 polling stations after the December election, a move initiated by Putin in response to complaints of ballot stuffing and fraudulent counts. Those elections saw his United Russia party retain its majority in parliament, though substantially reduced from its previous overwhelming control.
It was unclear Sunday to what extent the cameras would be effective in recording voting irregularities or questionable counts. The election observation mission of the Organization for Security and Cooperation in Europe noted skepticism in a report on election preparations.
"This is not an election ... it is an imitation," said Boris Nemtsov, another prominent opposition leader.