The Turkish policeman who assassinated Russia's ambassador was unlikely to have acted alone, a senior Turkish government official says, as investigators from both countries hunted for clues as to who might have been behind the killing.
Russian investigators arrived in the Turkish capital of Ankara on Tuesday morning and headed to the art gallery where Ambassador Andrei Karlov was shot dead on Monday evening by Mevlut Mert Altintas.
The 22-year-old gunman, a member Ankara's riot police squad, shouted slogans about the embattled Syrian city of Aleppo as he killed the envoy.
The senior government official described the killing as "fully professional, not a one-man action" and said the attack was well-planned. The official spoke on condition of anonymity.
Turkish authorities have not publicly released any information on the investigation or on a possible motive for the policeman.
Turkey and Russia, which have backed opposing sides in the Syrian war, vowed not to let the killing disrupt efforts to repair their ties.
"Strong relations will continue, no one has the strength to destroy the relationship" between the two countries, Turkish Prime Minister Binali Yildirim said during a speech in Istanbul.
Turkish President Recep Tayyip Erdogan said he and Russian President Vladimir Putin, with whom he spoke by phone Monday night, were "in agreement that this was an open provocation".
Karlov's assassination came after days of protests by Turks angry over Moscow's support for Syrian President Bashar Assad and Russia's role in the bombardment and destruction of rebel parts of Aleppo.
"Don't forget Aleppo! Don't forget Syria!" Altintas shouted during the attack, shooting Karlov.
The attacker was later killed by police.
Turkish police have detained seven people in connection with the policeman: his parents, sister, three other relatives and his roommate in Ankara, Turkey's state-run Anadolu news agency reported.
Turkish Foreign Minister Mevlut Cavusoglu, speaking at a previously scheduled meeting on Syria in Moscow with Russian Foreign Minister Sergey Lavrov and their Iranian counterpart, said Turkey and Russia would work together to determine who was behind the "heinous terror attack".
An Associated Press photographer and others at the art gallery watched in horror as Altintas, who was wearing a dark suit and tie, fired at least eight shots, at one point walking around the ambassador as he lay motionless and shooting him again at close range.
Authorities increased security outside the Russian Embassy, and the Iranian Embassy was closed Tuesday as a precaution.
Russia warned citizens against travelling to Turkey, citing attacks that have hit the country over the past 18 months.
