Turkey's President Recep Tayyip Erdogan has suffered a setback as the country's largest opposition prevailed over his ruling party in local elections nationwide.

Turkey held local elections across 81 provinces on Sunday.

The main issues in the campaign included the economy, which has been hit by chronic inflation and a weakening currency, and responses to a major earthquake in February last year that left over 53,000 people dead.

The government-affiliated Anadolu news agency said turnout stood at more than 78 percent. Over 98 percent of ballot boxes had been opened across the country as of 3:30 a.m. on Monday, local time.

The main opposition Republican People's Party led with more than 37 percent of the vote in mayoral elections, compared with over 35 percent for the governing Justice and Development Party.

In the capital Ankara and the country's largest city of Istanbul, the incumbent mayors of the main opposition party declared victory.

Erdogan spoke to supporters at the headquarters of the governing party on Monday. He said his party did not achieve the desired result, and he vowed to carry out self-criticism and address shortcomings.

The setback faced by Erdogan's party is thought to stem from public dissatisfaction with the sluggish economy and the government's recovery efforts following the earthquake.