The mayor, Ekrem Imamoglu, was detained after prosecutors accused him of corruption and terrorism. The opposition said the arrest was politically motivated.

As the detention of Istanbul's mayor and the arrest of more than 100 raise alarms over an escalating crackdown on opposition, internet access across Turkey has slowed and protests are banned in Istanbul.

Ekrem Imamoglu, the mayor of Istanbul and a popular figure, had boasted jokingly that he was the only person to have beaten Recep Tayyip Erdogan’s ruling party in three local elections.