St. Petersburg opposition groups applied on Tuesday for official permission to hold an anti-Putin rally in the city next month.
Five downtown locations including the city's iconic Dvortsovaya Square were envisaged as possible venues for the demonstration on June 12, the People's Freedom Party (Parnas) said in a statement.
Protesters claim President Vladimir Putin's landslide March 4 election victory was rigged.
A large demonstration is also planned in central Moscow.
The previous Moscow mass protest, on the eve of Putin's May 7 presidential inauguration, saw more than 400 arrests as demonstrators fought pitched battles with police.
The ruling United Russia party has since initiated a bill which massively increases fines for unapproved rallies. The bill drew condemnation from other parliamentary parties and opposition groups, but is still likely to be approved before the June 12 protests.
