Moscow's mayor has handed in his resignation to Russian President Vladimir Putin.
Sergei Sobyanin's move comes after he announced his intention on June 4 to run in an early election for the post in September.
Sobyanin was confirmed as Moscow mayor for five years in 2010.
Last year a law regulating regional elections was amended, allowing mayors to be elected by direct vote.
Sobyanin's move to force an early election is seen as harming his opposition challengers, including billionaire Mikhail Prokhorov and anticorruption crusader Aleksei Navalny, who may struggle to get their campaigns ready on short notice.
Russian television quoted Putin as telling Sobyanin on June 5 that he would like to see him "continue doing his work."
Sobyanin will be acting mayor until the election.
Based on reporting by AP, ITAR-TASS, and Interfax