The Turkish government has accused associates of US-based Muslim cleric Fethullah Gulen in the police and the judiciary of eavesdropping on thousands of people including Prime Minister Recep Tayyip Erdogan.
Erdogan has accused rivals in the influential Gulen group of acting as a "state within a state" seeking to topple his government by instigating a high-level corruption investigation against close allies.
On Monday, pro-government dailies Yenisafak and Star said classified documents revealing the surveillance were discovered by new prosecutors appointed after a mass purge of the police and prosecution service in the wake of the corruption probe launched in December.
Cabinet ministers, the country's spy chief and journalists were among the targets, according to the reports, which government spokesman Bulent Arinc confirmed to journalists.
"This a sad and shocking event. The public is following this closely," Arinc said.
Media sympathetic to Gulen quoted his lawyer Nurullah Albayrak as saying the allegations were "unfair". "The only purpose of this situation is to incite hatred and division," he said.
One of the former prosecutors Adnan Cimen also denied that anything illegal had taken place.
"These allegations are entirely without foundation. Not a single illegal operation was authorised," Cimen told newspaper Milliyet.
The Star reported that so-called Gulenists had wiretapped more than 7,000 people, as well as the headquarters of the opposition Republic People's Party (RPP), since 2011 on the pretext of trying to uncover terrorism plots.
Energy Minister Taner Yildiz said he had been wiretapped. Intelligence chief Hakan Fidan and one of his close allies were also among those targeted, along with many business people, activists and journalists, according to the newspaper reports.
The corruption scandal has thrown up one of the most serious challenges to Erdogan's 11 years in power ahead of key local elections in March.
The mass eavesdropping reports come as parliament began debating a new bill aimed at giving the intelligence agency a free hand in carrying out undercover missions and surveillance at home and abroad - without the need for a court order.
Erdogan has come under fire for what critics see as increasingly authoritarian policies, including curbs on the judiciary and the internet.
