Russian President Vladimir Putin has said the killing of the Russian ambassador to Ankara is aimed at undermining both Russian-Turkish relations and the Syrian peace efforts.
"This murder is clearly a provocation aimed at undermining the improvement and normalization of Russian-Turkish relations, as well as undermining the peace process in Syria promoted by Russia, Turkey, Iran and other countries interested in settling the conflict in Syria," said a stern-faced Putin on Monday evening.
The "only response" to the attack that Moscow "should offer" is "stepping up the fight against terrorism," the president added.
"The killers will feel it," Putin said.
In televised comments, Putin, speaking at a special meeting in the Kremlin, ordered security at Russian embassies around the world to be stepped up and said he wanted to know who had "directed" the gunman's hand.
He heaped praise on the murdered Russian ambassador, Andrei Karlov, who was shot in the back and killed as he gave a speech at an Ankara art gallery, and made clear that Moscow's response to his assassination would be robust.
Saying that ambassador Andrey Karlov "was a brilliant diplomat, widely respected in the country where he was posted," the president added the Russian diplomat "was in good standing with both the government of Turkey and other political groups in that country."
Putin, who said he personally knew the slain envoy, said he had agreed in a phone call with his Turkish counterpart Tayyip Erdogan that Russian investigators would soon fly to Ankara to help the Turks with the investigation.
"We must know who directed the killer's hand," Putin told Foreign Minister Sergei Lavrov, Sergei Naryshkin, the head of his SVR foreign intelligence service, and Alexander Bortnikov, the head of the domestic FSB security service.
A Turkish policeman on Monday fatally shot Russia's ambassador to Turkey on Monday in front of a shocked gathering at a photo exhibit and then, pacing near the body of his victim, appeared to condemn Russia's military role in Syria, shouting: "Don't forget Aleppo! Don't forget Syria!"
The assailant, who was identified as Mevlut Mert Altintas, a 22-year-old member of Ankara's riot police squad, was later killed in a shootout with police. Three other people were wounded in the attack, authorities said.
The assassination came after days of protests by Turks angry over Russia's support for President Bashar Assad in the Syrian conflict and Russia's role in the bombardment and destruction of Aleppo, Syria's largest city.
The gunman shouted about Aleppo in Turkish, and also yelled "Allahu akbar," the Arabic phrase for "God is great," continuing in Arabic: "We are the descendants of those who supported the Prophet Muhammad, for jihad."