Dozens of high-ranking police officers were detained in Turkey today (22 July) accused of involvement in spying and illegal wire-tapping during an investigation into corruption in Prime Minister Recep Tayyip Erdoğan's inner circle, CNN Turk said.

At least 76 officers were detained in 22 provinces around the country on suspicion of forming a criminal organisation and illegally bugging phones, the news channel said, weeks ahead of a presidential election in which Erdoğan is standing.

Other local media said most of those detained had held key positions during the corruption investigation, which emerged in December and led to the departure of four cabinet ministers and the detention of prominent businessmen close to Erdoğan.

Police in Istanbul declined to comment.

Erdoğan cast the corruption investigation as a plot to oust him orchestrated by a "parallel state" loyal to U.S.-based Islamic cleric Fethullah Gülen, a powerful preacher with influence in the police and judiciary.

He accuses Gülen's Hizmet ("Service") network of concocting the scandal by illegally wiretapping thousands of government phones and leaking manipulated recordings on social media.

His aides had made clear the fight against Hizmet would continue in the run-up to Turkey's first direct presidential election on 10 August, in which Erdoğan is the front-runner.

Thousands of police officers and hundreds of judges and prosecutors have already been reassigned and senior officials in state institutions dismissed since the investigation, in what is seen as a government drive to purge Gülen's influence. Gülen, who has lived in self-imposed exile in Pennsylvania since 1999, denies plotting against the government.