Istanbul, Jun 23 (IANS): Residents of Turkey's Istanbul city once again cast their votes on Sunday to elect a mayor after an opposition candidate's surprise victory in March was annulled.

Voting started at 8 a.m. and will continue through 5 p.m. in 31,342 ballot boxes across 39 districts of Istanbul, reports Hurriyat Daily News.

Ekrem Imamoglu, candidate of the opposition Republican People's Party (CHP), and former Prime Minister Binali Yildirim of the ruling Justice and Development (AKP), are the two main candidates the fray after a previous vote on March 31 was annulled by the country's top election council last month.

Millions of Turkish voters cast their votes nationwide on March 31 in local elections to choose mayors, city council members, 'mukhtars' (neighbourhood officials), and members of elder councils for the next five years.

On March 31, the turnout was 83.88 per cent, six percentage points lower than the previous local elections of March 30, 2014.

In Istanbul, Imamoglu received 48.8 per cent of the vote, whereas Yildirim got 48.55 per cent, according to official figures from the Supreme Election Council (YSK).

AKP won 24 district municipalities across the province, while the CHP won 14.

The results in March were cancelled after the AKP and its coalition partner, the Nationalist Movement Party (MHP), appealed to the YSK, citing irregularities and contradictions with legal measures, leading to the annulment of Imamoglu's mayoral certificate.

On the March 31 elections, voters chose from among 32 candidates - 24 of them independent - on the ballot.

This time, there will be only 21 candidates, including nominees from AKP, the CHP, the Felicity (Saadet) Party and the Patriotic (Vatan) Party along with 17 independent hopefuls.