Moscow, Jun 27 (IANS/RIA Novosti): Police in Russia's St. Petersburg city tried to prevent a group of Michael Jackson fans from commemorating the third death anniversary of the "King of Pop", citing a new law on public gatherings.

Jackson's fans have been gathering near the US consulate in St. Petersburg every year since the singer's death June 25, 2009, to mark his passing by lighting candles, putting up posters, singing and moonwalking.

The consulate has been supportive of the annual flash mob, as have police, but this year law enforcement took a different view of the event, according to city news website Baltinfo.ru.

Police tore down posters brought by fans who gathered near the consulate. They also threatened to slap hefty fines for an unsanctioned public gathering.

A police car followed the Jackson fans down a street, and one activist had to spend several hours in detention for staging an unauthorised rally.

Legislation on public rallies in Russia was radically tightened after regular anti-Kremlin protests were held in Moscow since December.

New rules hiked fines for violations at public events or staging unsanctioned rallies from 1,000 to 300,000 rubles.