Turkey's main opposition party has claimed big election victories in the main cities of Istanbul and Ankara.

The results are a significant blow for Recep Tayyip Erdogan, who had hoped to regain control of the cities less than a year after he claimed a third term as president.

He led the campaign to win in Istanbul, where he grew up and became mayor.

But Ekrem Imamoglu, who first won the city in 2019, scored a second victory for the secular opposition CHP.

Mr Erdogan had vowed a new era in Turkey's megacity of almost 16 million people, but the incumbent mayor of Istanbul secured more than 50% of the vote, defeating the president's AK Party candidate by more than 11 points and almost one million votes.