Updated

Moscow will hold mayoral elections two years early after Mayor Sergei Sobyanin said he supported holding a snap poll in the fall.

Sobyanin offered his resignation and said Tuesday that he backed moving the vote forward from 2015, when his current term expires, to Sept. 8.

Sobyanin hails from Siberia and never lived in Moscow before becoming President Vladimir Putin's chief of staff in 2005. He was appointed Moscow mayor by then-President Dmitry Medvedev in 2010.

The move is expected to harm his opposition challengers, including billionaire Brooklyn Nets owner Mikhail Prokhorov and anti-Putin firebrand Alexey Navalny, who may struggle to get their campaigns ready on short notice.

Some 54 percent of Muscovites would vote for Sobyanin, according to a poll Monday by a Kremlin-linked institute at Moscow State University.