At least 28 suspects have been arrested across Turkey on Tuesday over suspected links to the Fetullah Terrorist Organization (FETO), according to security officials.

Axar.az reports citing AA that, FETO and its U.S.-based leader Fetullah Gulen orchestrated the defeated coup attempt of July 15, 2016, which left 250 people martyred and nearly 2,200 injured.

In northern Samsun province, 13 people were arrested for using FETO’s encrypted smartphone messaging application ByLock, an official, who asked not to be named due to restrictions on talking to the media, told Anadolu Agency.

The app is believed to have been cracked by Turkish security agencies, allowing them to identify tens of thousands of FETO supporters within the context of last year's defeated coup attempt.

Six people -- some of them spouses of ex-police officers -- were caught after they were found to have used Bylock app, as part of a probe launched by Zonguldak Chief Public Prosecutor’s Office.

A former deputy tax inspector, whose arrest warrant was issued by Izmir prosecutor’s office, has been caught after he got involved in a traffic accident.

Separately, six members of the terrorist organization, who were attempting to cross into Bulgaria from Edirne province, were arrested along with three Bulgarian citizens, who were accused of helping them.

In a joint operation in northwestern Kocaeli, five on-duty soldiers were arrested.

Meanwhile, the Ministry for Family and Social Policy shut down FETO-linked 45 preschools across Turkey.

In the Black Sea province of Kastamonu, a former police officer was sentenced to six years and three months in prison for using ByLock and “being a member of a terrorist organization” by a high criminal court.

The 28th High Criminal Court in Istanbul convicted Oguz Guven, the editor-in-chief of cumhuriyet.com.tr, who was arrested on May 12.

Guven, who was accused of making terrorist propaganda, and disseminating terrorist publications, was sentenced to three years and one month in prison.