MOSCOW - Hundreds of riot police were on the streets of central Moscow Saturday as opposition protesters prepared to defy a crackdown by authorities and launch fresh demonstrations to demand to free local elections.

In a move to circumvent restrictions by the authorities, the activists were planning to let one person at a time hold a protest sign as such demonstrations do not technically need approval.

The wave of rallies has seen tens of thousands take to the streets after opposition figures were banned from local elections a month ago.

The rallies, which have taken place every Saturday since the ruling, are the biggest since mass protests broke out in 2011 against President Vladimir Putin's return to the Kremlin after a term as prime minister.

Police have come down hard on the demonstrations, which have tapped into wider anger over declining living standards and a stalling economy.

Some 3,000 people have been arrested for taking part and prominent members of the opposition, including top Kremlin critic Alexei Navalny, remain behind bars.

At previous events police have used batons against protesters and grabbed people from the streets indiscriminately.

Earlier around 4,000 people took part in an approved Communist Party rally for free elections, according to independent monitors.

The Communists are tolerated by the Kremlin and its veteran leader Gennady Zyuganov has said the party will not support the liberal opposition's protest.

Many protesters came to the Communist rally with red Soviet flags. Many were middle-aged, some years older than those in the opposition rallies.

Prosecutors have launched criminal cases against about a dozen protesters for "mass unrest", with potential prison sentences of up to eight years.

They stand accused of offenses including throwing plastic water bottles at officers.

The Moscow city hall elections set for September 8 were, until last month, a relatively minor event on Russia's political calendar.

But the issue blew up after election authorities refused to register various opposition candidates over alleged violations including faking the signatures needed to qualify.

Local polls are a rare opportunity for dissenting voices to participate in political life as anti-Kremlin parties have been squeezed out of parliament over Putin's two decades in power. -AFP