A large opposition rally, the first after Vladimir Putin's landslide victory in Russia's presidential elections, is underway in Moscow Monday.

According to official police reports about 5 500 are attending the approved protest rally on Pushkin Square, a short walk from the Kremlin, but western media, including BBC, list the number at 14 000.

They have gathered in front of a stage, wrapped in a sign reading "For Fair Elections."

The Coalition of the Russian opposition demands snap presidential elections and calls Putin's Sunday victory a "farce."

Over 12 000 police are deployed to ensure order. Some 120 arrests have been reported at rallies against Putin in Moscow and in his home city of St Petersburg. Another 50 people were arrested at a separate protest on Moscow's Lubyanka Square, where the headquarters of the Federal Security Service is located, BBC informs.

Hundreds of protesters also marched in Yekaterinburg, the main city in the Urals, chanting "Putin thief!"

A rally in support of the President-elect is held on Manege Square, beside the Kremlin, with reports of about 14 000 people attending as well, and in a number of Russian cities.

On Monday, Russia's electoral commission said that with 98% of the votes counted, Putin won 64%, enough to give him a first-round victory over nearest rival Communist Party leader, Gennady Zyuganov, who polled about 17%

The other three candidates were in single digits.