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

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.

Mayor Ekrem Imamoglu of Istanbul is the top political rival of President Recep Tayyip Erdogan, and was set to be named the opposition’s presidential candidate.