Turkish President Recep Tayyip Erdogan conceded defeat on Sunday in the country's local elections, saying the vote was a "turning point" for his party after two decades in power.

Partial results from across Turkey showed major advances for the Republican People's Party (CHP) at the expense of Erdogan's Justice and Development Party (AKP).

Istanbul's mayor, the opposition's Ekrem Imamoglu, claimed re-election with nearly all ballot boxes opened, telling a euphoric crowd of supporters: "Tomorrow is a new spring day for our country."

Erdogan, 70, had launched an all-out personal campaign to win back Istanbul, the economic powerhouse where he was once mayor. Rampant inflation and an economic crisis have, however, hit confidence in the ruling party. (AFP)