Voting, which started at 8.00 a.m. local time (0500GMT) continued through 5.00 p.m. local time (1400GMT) in 31,342 ballot boxes across 39 districts of Istanbul.
Ekrem Imamoglu, candidate of the opposition Republican People's Party (CHP), and Binali Yildirim of the ruling Justice and Development (AK) Party, vied to run the metropolitan municipality of Turkey's most populous city after a previous vote on March 31 was annulled by the country's top election council last month.
According to the ban imposed by the Supreme Election Council (YSK), media organizations will not be allowed to broadcast any political advertising, predictions or comments about the polls from 6 p.m. local time (1500GMT) until 9 p.m. (1800GMT).
The YSK reserves the right to lift the broadcasting bans before 9 p.m. on Sunday.
Millions of Turkish voters cast their votes nationwide on March 31 in local elections to choose mayors, city council members, mukhtars (neighborhood officials), and members of elder councils for the next five years.
On March 31, the turnout was 83.88%, six percentage points lower than the previous local elections of March 30, 2014.
In Istanbul, Imamoglu received 48.8% of the vote, whereas Yildirim got 48.55%, according to official figures from the Supreme Election Council (YSK).
AK Party won 24 district municipalities across the province, while the CHP won 14.
The results in March were canceled after AK Party 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.
YSK chief Sadi Guven said all eligible voters who cast their ballots in the March 31 poll would be able to do so again in a re-do vote for Istanbul’s metropolitan mayor.
In the election rerun on Sunday, AK Party's and CHP’s YSK representatives pointed out confusion caused by use of some stamps that were also used in the last parliamentary elections.
Also, some unsealed ballot envelops were found in some districts, according to both parties’ representatives.
Recep Ozel, AK Party's YSK representative, and Mehmet Hadimi Yakupoglu, CHP’s YSK representative asked the YSK to deem those votes valid.
YSK ruled the will of the voters will not be affected by this and the votes will be counted valid.