Turkey arrested a former police officer for suspected connection with assassination of former Russian Ambassador to Turkey Andrei Karlov in 2016, daily Hurriyet reported Thursday.

The police officer Ufuk G. was suspected of being a member of the same terror organization with the assassin Mevlut Mert Altintas.

Ufuk G. reportedly refuted the accusations.

Andrey Karlov was killed by Altintas, then an off-duty police officer, when delivering a speech at an art exhibition in Turkey's capital Ankara on Dec. 19, 2016.

Altintas was later shot dead in an exchange of fire with security personnel.

About five people have been detained so far, including three police officers and Guru Media Broadcast Group Chairman Hayreddin Aydinbas.

The investigation focused on links of the assassin with what Turkish authorities labelled as the Fethullahist Terrorist Organization.

The authorities believe that the group is headed by U.S.-based cleric Fethullah Gulen, who is accused by Ankara of masterminding the 2016 failed coup attempt against Turkish President Recep Tayyip Erdogan.