TURKISH authorities detained the mayor of a key Istanbul district along with 40 other officials today, intensifying a sweeping crackdown on the country's opposition.

Beyoglu Mayor Inan Guney was taken into custody as part of an investigation into alleged corruption, the state-run Anadolu Agency reported. Mr Guney’s bodyguard, his adviser and other aides were among those detained, according to the Birgun newspaper and other media.

The Beyoglu district is held by the main opposition Republican People’s Party (CHP). Local authorities controlled by the CHP have faced waves of arrests this year, beginning with the detention of Istanbul Mayor Ekrem Imamoglu in March.

Mr Imamoglu is considered Mr Erdogan’s most challenging rival for the presidency and his arrest sparked the biggest protests across Turkey for over a decade. Opposition forces say the arrests are part of a political crackdown, while the government says the courts and police operate independently.