The two leading contenders for Istanbul mayor are set to face off in a debate a week before a repeated city election.

The debate between Binali Yildirim, the candidate from Turkey's ruling Justice and Development Party, or AKP, and secular opposition candidate Ekrem Imamoglu of the Republican People's Party, or CHP, was to be broadcast live on Sunday.

Imamoglu, a former district mayor, narrowly won a March 31 election. But Turkey's election authority annulled the vote after the Justice and Development Party challenged the result, citing a breach of voting regulations.

Televised election debates are uncommon in Turkey. The last one, between AKP leader Recep Tayyip Erdogan and the then-leader of the CHP, took place before a 2002. The AKP has been in power since. Erdogan is Turkey's president.