Turkish authorities have detained Istanbul Mayor Ekrem Imamoglu, a key rival to President Recep Tayyip Erdogan, as part of corruption and terror investigations, according to state broadcaster TRT, citing the Istanbul Prosecutor’s Office.

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.