Ten out of 29 suspects were arrested as part of an investigation into the infiltration of Fetullah Terrorist Organization (FETÖ) into the Turkish Foreign Ministry missions in Europe, according to a security source on Saturday.

The suspects were sought with warrants issued by top prosecutors in the Turkish capital Ankara, after police teams of combatting financial crimes found that a Foreign Ministry staff on active-duty was using ByLock, the encrypted smartphone messaging app of FETÖ, the group behind the 2016 deadly defeated coup in Turkey.

It forced the police extend the probe to discover a ByLock group -- named “Marketing People” which was created by E. S., the covert imam or senior FETÖ member secretly operating at the ministry.

Upon update of the authorities at the Foreign Ministry, officials identified the FETÖ members, which included suspects working at Riyadh, Berlin, and Paris embassies, as well as those who previously worked at embassies in Europe and continued their duty in Ankara.

The operation was initiated in early hours of Saturday in Ankara, Istanbul and Bursa provinces and it arrested 10 suspects, five of whom were on-duty officials.

Among the suspects was a dual national with Turkish and German citizenship. The suspect was found to be in contact with everyone in the ByLock group and thought to be the “Europe representative” of FETÖ.

The operation was carried out by the police teams for nearly four months and all phases were kept confidential.