On Saturday, nearly 1,400 people were arrested at an unauthorised protest in Moscow against the exclusion of opposition politicians from local  elections later this year.

"Prosecutors should in a severe manner prevent the actions of organisers and participants in illegal and unsanctioned public rallies," prosecutor Alexander Buksman was quoted as saying by state news agency RIA Novosti.

He also urged extra vigilance in the run-up to the local elections in September.

Following the mass arrests at the weekend, the West has condemned the largest police crackdown on dissent in Russia in recent years.

Ahead of Saturday's rally, police jailed opposition leader Alexei Navalny for 30 days and detained a number of popular independent politicians who have fought to get on the ballot.

They included the director of Navalny's Anti-Corruption Fund, Ivan Zhdanov, who on Monday was sentenced to 15 days in jail.

Prominent opposition politician and another would-be candidate Ilya Yashin said Tuesday he had been sentenced to a further 10 days in jail, after receiving a  10-day sentence the day before.

The opposition has called for a new protest on Saturday, with  nearly 13,000 people on Facebook indicating interest in that rally.