MOSCOW (Reuters) - Russian opposition activists staged a string of pickets in central Moscow on Saturday to call for free elections and for charges against protesters detained at recent rallies to be dropped.

Moscow has been rocked by weekly protests for more than a month since the authorities barred opposition candidates from running in an election for the city’s legislature in September.

Police have briefly detained more than 2,000 protesters in recent weeks, launched criminal cases against some dozen people for mass disorder and used force to disperse what they said were illegal protests.

In contrast Saturday’s solo pickets, spread across three locations in Moscow, were peaceful and opposition supporters scarce.

The recent opposition demonstrations have turned into the biggest sustained protest movement in Russia since 2011-2013, when protesters took to the streets against perceived electoral fraud.

Earlier on Saturday some 4,000 people attended a Communist rally in Moscow that had been authorized by the authorities to call for “clear and honest elections” in Moscow, police said.