FILE PHOTO: People wave Turkey's national flags as they attend a ceremony marking the first anniversary of the attempted coup at the Bosphorus Bridge in Istanbul, Turkey July 15, 2017. REUTERS/Murad Sezer

ANKARA (Reuters) - Turkish authorities issued detention warrants for 79 former school employees on Wednesday over alleged links to last year’s failed military coup, broadcaster NTV said.

They were suspected of using ByLock, an encrypted messaging app which the government says was used by the network of U.S.-based cleric Fethullah Gulen, whom it accuses of orchestrating the abortive putsch in July 2016.

The suspects worked at private schools and tutor schools which prepared students for university entrance exams, many of which used to be run by supporters of Gulen.

Gulen, who has lived in self-imposed exile in the United States since 1999, has denied involvement and condemned the coup attempt.

Since the coup attempt some 150,000 people have been sacked or suspended from jobs in the public and private sectors, including some who worked at schools founded by his supporters, and more than 50,000 have been detained for alleged links to it.

The crackdown has alarmed rights groups and some of Turkey’s Western allies, who fear the government is using the coup as a pretext to quash dissent.

The government, however, says Gulen’s network deeply infiltrated Turkey’s institutions - the army, schools and courts - and only a massive purge could neutralize the threat.