The shocking assassination of Russia's ambassador in Ankara on Monday – the first murder of a foreign diplomat in Turkey in decades – threatened to rupture fragile relations between the two countries, critical to a peaceful resolution of the Syrian conflict.
The veteran diplomat was shot in the back by a 22-year-old off-duty policeman who cited revenge over Russia's policies in Aleppo, Syria's largest prewar city whose last rebel bastions were recently overtaken by the army of Russian-supported dictator Bashar al-Assad.
"Do not forget Aleppo! Do not forget Syria!" the gunman shouted in dramatic video of the attack's aftermath. He was killed in a shootout with police.
Ambassador Andrei Karlov was giving a speech for the opening of a Russian embassy-sponsored exhibit at an Ankara art gallery. The gunman, who was wearing a dark suit and tie, fired at least eight shots, at one point walking around Mr. Karlov as he lay motionless and shooting him again at close range.
The spectacle of 62-year-old Mr. Karlov's assassination by a member of the Turkish security forces at a photography show meant to highlight Russian culture reinforced the sense of unease over the region's conflict and complex web of alliances and relationships.
Turkish President Recep Tayyip Erdogan and Russian President Vladimir Putin spoke by phone shortly after the shootout
"This is a provocation to damage the normalization process of Turkish-Russian relations. But both the Russian and Turkish administrations have the determination not to fall for this provocation," Mr. Erdogan in said in a video message, adding that a joint Russian-Turkish commission would be formed to investigate the murder.
"We must know who was directing the killer," Mr. Putin said.
In a sign of just how much Russian-Turkish relations have evolved since last year, when Turkey's downing of a Russian bomber jet over the Syrian border came close to escalating into a shooting war, the two regional rivals called the killing a provocation and vowed not to let it undermine the emerging co-operation between them.
Moscow and Ankara need each other as they seek to negotiate a ceasefire in Syria, something that would increase their international status and leverage in the war-torn country at the expense of the West.
In recent weeks, with the United States preoccupied in a messy presidential transition, Turkey and Russia have made attempts to negotiate a solution to the Syrian crisis without the United States and the United Nations. The evacuation of Turkish-backed rebels and civilians from eastern Aleppo is proof of that.
The gunman in Monday's attack was identified as Mevlut Mert Altintas, a member of Ankara's riot police squad. Three other people were wounded in the attack, authorities said.
Hours after the assassination, pro-government media in Turkey were flush with speculations, fed by comments from anonymous officials, that the attack was carried out on behalf of Fethullah Gulen, a charismatic Muslim preacher living in Pennsylvania. Mr. Gulen, who has denied the allegation, is blamed for a failed military coup in July – in which he also denies involvement – and Ankara has sought his extradition ever since.
The Turkish government believes thousands of Gulen followers have infiltrated the country's institutions. Over several months, members of the Turkish military, police, judiciary and academia have been arrested for alleged links to the Gulen organization.
On Tuesday, the Turkish-Russia relationship will face its first test in the wake of the assassination. A three-way summit between Turkey's Foreign Minister and his Russian and Iranian counterparts is to take place in Moscow. Iran is the other main backer of the Assad regime.
Russia has been seeking an end to Turkish-backed efforts to bring down Mr. al-Assad's government while, in recent months, Turkish goals have appeared to subtly shift toward building a buffer zone in northern Syria, where it sent forces to drive away the Islamic State group this summer. Such a safe zone could be home to refugees and rebels.
The murder of the Russian ambassador could hurt Turkey's leverage in the Moscow talks.
"If anything, [the attack] will increase [the] intelligence and security partnership between the two countries," said Hamid Akin Unver, an assistant professor of international relations at Kadir Has University in Istanbul.
"Yet, the incident impairs Ankara's ability to diplomatically pressure Russia … and furthermore, it opens up more extensive pressuring channels for Moscow to force Ankara to end any and all proxy relations into Syria, effectively cutting off Ankara from Aleppo or its aftermath," he added.
Mr. Erdogan and other Turkish officials have said they would build camps to house refugees from Aleppo and possibly other parts of Syria in the areas liberated from the Islamic State group. Experts have said previously that this could even offer a way out of the standoff between the European Union and Turkey over the flow of refugees by allowing Ankara to move refugee camps from its territory to the buffer zone. Key to Turkey's hope of creating a Syrian buffer zone is getting Russia's buy-in.
With a report from Associated Press