Moscow Mayor Sergei Sobyanin has handed in his resignation to President Vladimir Putin, forcing an election in the fall in which he likely will be returned to the job.

Sobyanin was appointed mayor by then-President Dmitry Medvedev in 2010 at a time when it was an unelected post. The Russian government has since restored the direct election of mayors.

The move to force an early election — Sobyanin's term ran until 2015 — is seen as harming his opposition challengers, including billionaire Brooklyn Nets owner Mikhail Prokhorov and anti-corruption crusader Alexei Navalny who may struggle to get their campaigns ready on short notice.

Russian television on Wednesday quoted Putin telling Sobyanin that he would like to see him "continue doing his work." Sobyanin will be acting mayor until the election.