Turkish President Tayyip Erdogan has accepted defeat after the opposition made major gains in the country’s local elections on Sunday.

Erdogan has called the election a ‘turning point’ and said that he accepts the verdict of the people.

With most of the votes counted, Imamoglu led by 10 percentage points in the mayoral race in Istanbul, Turkey’s largest city, while his Republican People’s Party (CHP) retained Ankara and gained 15 other mayoral seats in cities nationwide.

It marked the worst defeat for Erdogan and his AK Party (AKP) in their more than two decades in power, and could signal a change in the country’s divided political landscape. Erdogan called it a “turning point” in a post-midnight address.

He and the AKP fared worse than opinion polls predicted due to soaring inflation, dissatisfied Islamist voters and, in Istanbul, Imamoglu’s appeal beyond the CHP’s secular base, analysts said.

“Those who do not understand the nation’s message will eventually lose,” Imamoglu, 53, told thousands of jubilant supporters late on Sunday, some of them chanting for Erdogan to resign.

“Tonight, 16 million Istanbul citizens sent a message to both our rivals and the president,” said the former businessman, who entered politics in 2008 and is now widely touted as a likely presidential challenger.

Erdogan, who in the 1990s was also mayor of his hometown Istanbul, had campaigned hard ahead of the municipal elections, which analysts described as a gauge of both his support and the opposition’s durability.

Addressing crowds gathered at AKP headquarters in Ankara, the capital, Erdogan said his alliance had “lost altitude” across the nation and will take steps to address the message from voters.

“If we made a mistake, we will fix it” in the years ahead, he said. “If we have anything missing, we will complete it.”

Elsewhere in Ankara, thousands more supporters had earlier waved Turkish and party flags for a speech by reelected CHP Mayor Mansur Yavas, who trounced his AKP challenger in another disappointment for Erdogan.

According to 92.92% of ballot boxes opened in Istanbul, Europe’s largest city and the country’s economic engine, Imamoglu had 50.92% support compared with 40.05% for AKP challenger Murat Kurum, a former minister in Erdogan’s national government.

Polls had predicted a tight contest in Istanbul and possible CHP losses across the country. Yet partial official results reported by state-run Anadolu Agency showed AKP and its main ally giving up mayoralties in 19 key municipalities including big cities Bursa and Balikesir in the industrialised northwest, possibly reflecting strains on wage earners.

The CHP led nationwide by almost 1% of the votes, a first in 35 years, the results showed.