MOSCOW (AFP) - The Communist Party won a surprise victory against President Vladimir Putin's ruling party in a mayoral race in Russia's third largest city of Novosibirsk, election officials said on Monday.

Communist lawmaker Anatoly Lokot won 43.75 per cent of the vote against the acting mayor Vladimir Znatkov from the ruling United Russia party, who took 39.57 per cent, the Siberian city's electoral commission said.

"We have created a unique situation in Russia where a united opposition managed to claim victory over United Russia," Lokot was quoted as saying on the Communist Party website.

Lokot won after another opposition candidate, Ilya Ponomaryov, from the left-leaning A Just Russia party, quit the race and told his supporters to back Lokot as the single opposition candidate.

"We did what no one believed could happen. We united and claimed victory...

The enemy is laid low. The red flag is raised over Siberia," Ponomaryov wrote in a blog on the website of Echo of Moscow radio station.

Ponomaryov has coordinated a number of anti-Putin protests and was the only lawmaker last month to vote against incorporating Crimea into Russia.

Novosibirsk, a city of 1.5 million residents around 2,800km east of Moscow, is famed as a scientific centre with a renowned university.