Turkey has arrested six people in connection with the assassination earlier of Russia’s ambassador to the country.

An off-duty police officer in civilian clothing, identified as 22-year-old Mevlut Mert Altintas, shot down Andrey Karlov, the Russian envoy, as he was inaugurating a photo exhibition in the Turkish capital, Ankara, on Monday.

On Tuesday, the state-run Anadolu agency said the attacker’s mother, father, sister and two other relatives were being held in the western province of Aydin, while his flatmate in Ankara had also been detained.

Kremlin spokesman Dmitry Peskov also said on Tuesday that Russian investigators had flown to Turkey earlier in the day to help probe the killing as per a mutual decision taken by Russian President Vladimir Putin and Turkish President Recep Tayyip Erdogan.

“Eighteen people will work in the group. The group will act in Turkey within the framework of the investigation into the murder,” Peskov said.

After carrying out the murder, the assailant went on a rant caught on camera, which saw him bawling, “Don’t forget Aleppo, don’t forget Syria!”

This picture, taken on December 19, 2016 in the Turkish capital, Ankara, shows guests leaving a gallery as a gunman (C) holds a weapon, during an attack where Andrey Karlov, the Russian ambassador to Ankara, was shot. (By AFP)

However, a senior Turkish security official has said there are “very strong signs” that the gunman belonged to the network of the US-based cleric Fethullah Gulen.

The Turkish establishment accuses Gulen, Erdogan’s ally-turned-archfoe, of orchestrating an abortive July coup.

The assassination, condemned by the Turkish and Russian leaders as an attempt to sour the bilateral ties, came as the countries are maintaining cooperation over the Syrian crisis. Turkey is partaking in talks on behalf of anti-Damascus militants, who had been holding the city until recently. Russia has been supporting the Syrian government and has been negotiating on its behalf.

Iran, the US, NATO, and other countries and world institutions have also condemned the assassination of the Russian ambassador.