Police yesterday arrested a new suspect in the investigation into the murder of Andrey Karlov, the former Russian Ambassador in Ankara, in 2016.

Karlov was assassinated by Mevlüt Mert Altıntaş, an off-duty police officer linked to Gülenist Terror Group (FETÖ) while attending an exhibition at an art gallery in Ankara.

The arrested suspect, identified by his initials H.T., is also a former police officer. He was charged with membership of a terrorist group. Turkish media outlets claimed that the suspect acted as a "brother" for Altıntaş and his roommate Sercan Başar, which is one of many terms used for FETÖ's handlers for the group's infiltrators in the law enforcement.

The Turkish language daily, Sabah said the arrested individual used the code name "Saya" while serving in the terrorist group and was also a donor to the group.

Altıntaş was killed in a shootout with police in the gallery where he murdered Karlov. Authorities have arrested seven people so far in their investigation of the case, including three former policemen, the exhibition's curator Mustafa Timur Özkan, and Hayreddin Aydınbaş, head of a media company.

The assassination occurred at a time of thaw between strained Turkish and Russian relations. Since the murder, Ankara and Moscow gradually made progress in rebuilding their ties, which were derailed by the 2015 downing of a Russian fighter jet over the Syrian border by the Turkish military.