A potential Imamoglu win would fuel expectations of him becoming a future national leader. However, polls suggest a tight race in the capital city of 16 million people, as Imamoglu faces a challenge from AKP candidate Murat Kurum, a former minister.

Polling stations opened at 7 a.m. (0400 GMT) in eastern Turkey and elsewhere at 8 a.m., with more than 61 million people registered to vote. Voting ends at 5 p.m. and initial results are expected by 10 p.m. (1900 GMT).