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

Political opposition leader and Istanbul Mayor Ekrem Imamoglu was in Turkish police custody Wednesday after he was arrested days before being chosen as the presidential candidate for the Republican People's Party.

Critics say the crackdown follows significant losses by Recep Tayyip Erdogan’s ruling party in local elections last year amid growing calls for early national elections.