Turkish President and Chairman of the Justice and Development Party (AK Party) Recep Tayyip Erdogan delivers a speech during the AK Party's group meeting at the Grand National Assembly of Turkey (TBMM) in Ankara, on October 3, 2017. (AFP Photo)

ISTANBUL, Oct. 3 (Xinhua) -- Turkish prosecutors issued detention warrants for 254 Istanbul municipality and ministry staff over alleged Gulen links, state-run Anadolu news agency reported Tuesday.

The operations mark a fresh escalation against the movement of Islamic preacher Fethullah Gulen, more than 14 months after the failed coup.

The Interior Ministry said on Monday nearly 1,000 people were detained over the previous week on allegations of ties to the "Gulenist Terror Group."

In Istanbul, prosecutors ordered the arrest of 112 current and former staff of municipalities in the Turkey's largest city, Anadolu agency reported.

They were accused of being users of Bylock, an encrypted messaging app which the government says was used by Gulen's followers.

Thirty-five of these suspects have so far been detained in the operation, stretching across eight provinces, Anadolu said.

Prosecutors in Ankara ordered the detention of 142 staff of the education and sport ministries, the agency said. The vast majority of them had already been dismissed from their jobs over alleged Gulen ties.

Gulen, who has lived in self-imposed exile in the United States since 1999, has denied involvement in the July 15 coup, in which 250 people were killed.