Russia's relationship with Turkey will not be threatened by the assassination of its ambassador in Ankara, its government says.
The ambassador, Andrei Karlov, was shot dead by an off-duty Turkish police officer at an art gallery in the Turkish capital.
Russia has described the killing as an act of provocation aimed at derailing Russian-Turkish relations and peace efforts in Syria.
Leonid Slutsky, who heads the international affairs committee in the Russian Parliament, said the shooting was a horrendous tragedy.
Mr Slutsky said while Russia's opponents in the West and in Turkey would be hoping for a cooling in relations, that would not be happening despite differences between the two countries over the ongoing conflict in Syria.
The Russian Foreign Ministry said it regarded the killing as a terrorist attack. A spokeswoman, Maria Zakharova, also said the attack would not derail the countries' relationship.
"Terrorism will not pass, we will fight it resolutely. The memory of this outstanding Russian diplomat, a man who did so much to counter terrorism in his diplomat line of work, Andrei Karlov, will remain in our hearts forever."
Ms Zakharova said Turkey had assured Russia there would be a thorough investigation into the shooting.
Turkey's President Recep Tayyip Erdogan said the assassination was an attack on his people's nation.
Gunman heard shouting
Mr Karlov was killed while making a speech at an exhibition at the Modern Art Centre in Ankara. The gunmen yelled "don't forget about Aleppo".
The Russian Foreign Ministry said the ambassador was taken to hospital but died of his wounds.
The killer has been identified as Mevlut Mert Aydintas, 22, a member of Ankara's riot police, who was off duty at the time. It was not clear if he had links to any extremist group.
News agency Anadolu said the gunman had been "neutralised", apparently killed.
Several other people were reportedly injured in the attack, a day after protests in Turkey over Russia's military intervention in Syria.
The ambassador was attending a photo exhibition at the gallery called "Russia as seen by Turks".
The attacker was smartly dressed and stood, alone, behind the ambassador as he made the speech.
Video of the event shows Mr Karlov delivering his speech when gunshots ring out.
The camera pulls back to show the gunman, wearing a suit and tie, waving a pistol and shouting.
He can be heard yelling "Don't forget about Aleppo, don't forget about Syria" and uses the Islamic phrase "Allahu Akbar" (God is great).
Another image shows four people including the ambassador lying on the floor.
Gunman's links unknown
It was not clear whether the gunman was a lone operator, driven perhaps by popular discontent over Russian action in Syria, or affiliated to a group like Islamic State, which has carried out a string of bomb attacks in Turkey in the last year.
Since a failed coup in July, President Erdogan has been purging the police of supporters of an exiled cleric and former ally, Fethullah Gulen, whom he characterises as the chief terrorist threat to Turkey.
Foreign and defence ministers of Russia, Iran and Turkey were due to discuss the future of Syria in Moscow on Tuesday. Leonid Slutsky, the chairman of the State Duma, said the talks would go ahead despite the killing of the ambassador.
While there were protests in recent days, on a political level the Turkish and Russian governments have been co-operating in the ceasefire operation in the Syrian city of Aleppo.
Mr Karlov, 62, was a veteran diplomat who had served as Soviet ambassador to North Korea for much of the 1980s.
After the fall of the USSR in 1991, he had a posting as Russian ambassador to South Korea before returning to the North for five years in 2001.
Taking up the Ankara posting in July 2013, he had to grapple with a major diplomatic crisis last year when a Turkish plane shot down a Russian jet close to the Syrian border.
The two countries only recently mended ties after Moscow imposed damaging sanctions - notably a freeze on charter flights by Russian tourists - demanding a Turkish apology.
-Reuters / BBC