Turkey detained Istanbul mayor Ekrem Imamoglu, the main rival of President Tayyip Erdogan, on charges of corruption and aiding a terrorist group in what the main opposition party on Wednesday called "a coup against our next president".

Turkish police have detained the strongest rival to President Recep Tayyip Erdogan, a move that experts say is aimed at removing all possible contenders ahead of the next presidential election and further stretching his rule.

Protests have erupted in Turkey after authorities detained the mayor of Istanbul, just days before he was due to be selected as a presidential candidate. Ekrem Imamoglu, from the secular Republican People's Party (CHP), is seen as one of President Recep Tayyip Erdogan's strongest political rivals.