Russia's ruling party appears to have won Sunday's local elections, but opponents are alleging widespread voting violations that will preserve President Vladimir Putin's dominance.

The Central Elections Commission said Monday early results showed United Russia heading for victory in all five provincial elections for governor. The ruling party had nearly 5,000 candidates running for office around the country.

But observers from the independent monitoring group Golos said the nationwide vote was marred by fraud, including multiple voting and ballot-stuffing. Leaders of United Russia — a party that has dominated Russian politics for more than a decade — have denied cheating.

Prime Minister Dmitri Medvedev, to whom Mr. Putin handed the chairmanship of United Russia after they swapped jobs, said the ruling party had done better than in a December parliamentary election in which it lost dozens of seats.

A round of protests began in December when disgruntled voters expressed their dismay in Moscow and other cities over Mr. Putin's plan to return to the presidency after four years as prime minister. The protests have recently died down.