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.

Critics say the arrest of Istanbul's mayor is part of a mounting crackdown by Turkey's president to silence all dissent.

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.