Alexei Navalny, the anti-corruption crusader who has spearheaded opposition to Russian President Vladimir Putin, plans to run for mayor of Moscow.

Navalny, one of the leaders of the anti-Putin demonstrations that rose up in late 2011, submitted documents to register his candidacy on Saturday, Russian news agencies cited the city elections commission as saying.

He was nominated by the liberal opposition RPR-Parnas party on Friday, saying he was entering the Sept. 8 election "to pull our city from the tentacles of Putin."

Moscow Mayor Sergei Sobyanin resigned last week, forcing a snap election in which he likely will be returned.

Sobyanin was appointed by then-President Dmitry Medvedev in 2010. Russia later restored mayoral direct election.

The early election could undermine challengers who may struggle to organize campaigns on short notice.