A former prime minister backed by Turkey’s ruling party has conceded defeat and congratulated his opponent in Istanbul’s repeated mayoral election.

Binali Yildirim said on Sunday night that opposition candidate Ekrem Imamoglu was ahead as the first returns were announced.

Turkey Istanbul Election
Binali Yildirim mayoral candidate for Istanbul (Emrah Gurel/AP)

Mr Yildirim said: “I congratulate him and wish him success.”

With nearly all votes counted, Mr Imamoglu had a lead of more than 715,000 votes.

Mr Imamoglu narrowly won office as mayor of Turkey’s largest city on March 31 and served for 18 days.

Turkey’s electoral board annulled the results after weeks of partial recounts.