ISTANBUL (Reuters) - Turkish authorities issued detention warrants for 170 people suspected of links to the network accused of orchestrating a failed coup in 2016, the state-run Anadolu news agency said on Tuesday.

Those targeted in the operation, which was centered in Istanbul and spread across 37 other provinces, included retired, suspended and serving soldiers, Anadolu said, adding 22 of them were detained on Tuesday morning.

The suspects are believed to have contacted imams of the network via payphones and landlines, the news agency said. The arrests are part of Turkey’s far-reaching crackdown against the network of U.S.-based Muslim cleric, Fethullah Gulen, whom Ankara holds responsible for the failed putsch.

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

In the 19 months since the coup attempt - when rogue soldiers commandeered tanks and warplanes to attack parliament, killing more than 240 people - Turkey has jailed more than 50,000 under a state of emergency. It has also sacked or suspended 150,000 people from their jobs in the military, public and private sectors.

The government dismisses rights groups’ concerns about the crackdown, saying only such a purge could neutralize the threat represented by Gulen’s network, which it says infiltrated institutions such as the judiciary, army and schools.