Over 100 people were detained in Istanbul while arrest warrants were issued in Ankara for more than 150 other suspects on Friday as part of ongoing investigations into the Gülenist Terror Group (FETÖ).

Police detained 115 people in Istanbul's Ümraniye and Üsküdar districts for suspected links to FETÖ, according to a police source.

The Chief Public Prosecutor's Office in Istanbul had earlier issued arrest warrants for 168 people as part of its FETÖ probe, out of whom 115 people were arrested, the source, who spoke on condition of anonymity due to restrictions on talking to the media, said.

Some suspects also allegedly used the ByLock mobile app that had been used by FETÖ members during the July 15, 2016, defeated coup, the source added.

ByLock is believed to have been cracked by Turkish security agencies, allowing them to identify tens of thousands of apparent FETÖ supporters.

Meanwhile, the Chief Public Prosecutor's Office in Ankara issued arrest warrants for 20 personnel of the Forestry and Water Affairs Ministry as part of its probe into FETÖ, according to a judicial source.

Out of the 20, six were on active duty while the rest had either been dismissed or temporarily suspended from their service, the source, who spoke on condition of anonymity due to restrictions on talking to the media, said.

Arrest warrants were also issued for 34 others who used to work at media outlets such as the Zaman daily, Taraf newspaper, Cihan news agency and Nokta magazine that had been shut down under statutory decrees.

All the suspects allegedly used the ByLock app, the source said.

The Chief Public Prosecutor's Office in Ankara also issued arrest warrants for 105 former police officers of various ranks in 13 different provinces as part of another FETÖ investigation on the charge of alleged use of the ByLock app.

FETÖ and its U.S.-based leader Fetullah Gülen orchestrated the defeated coup which left 250 people martyred and nearly 2,200 injured.

Ankara also accuses FETÖ of being behind a long-running campaign to overthrow the state through the infiltration of Turkish institutions, particularly the military, police and judiciary.