ISTANBUL (AP) — The mayor of Istanbul has announced his resignation as head of the city of nearly 15 million people.

Kadir Topbas, a member of President Recep Tayyip Erdogan's ruling party, declared he was stepping down during a televised news conference Friday. He did not provide a reason.

The resignation, however, came after the 72-year-old Topbas vetoed five zoning plan changes in the city but was overturned by members of his own party.

Topbas had been mayor of Turkey's financial capital and largest city since 2004. He reportedly fell from grace after his son-in-law was arrested last year for alleged ties to the movement led by U.S.-based cleric Fethullah Gulen, whom Turkey blames for the 2016 failed coup. Gulen denies the claim.

Topbas said he was not resigning from the party.