Karlov was shot while making a speech at the opening of an exhibition at an art gallery by a gunman who shouted in Turkish: "Don't forget Aleppo. Don’t forget Syria. Unless our towns are secure, you won’t enjoy security. Only death can take me from here. Everyone who is involved in this suffering will pay a price.”
The gunman later died after a shoot out with the police. According to Reuters, he was a Turkish riot police officer.
Russia and Turkey have been involved in opposing sides of the conflict in Syria, and tensions have increased in recent weeks as Russian-backed Syrian forces fought for control in Aleppo.
The mayor of Ankara, Melih Gokcek, said the attack was an attempt to ruin Turkish relations with Moscow.
President of the European Parliament Martin Schulz said he condemned the attack and gave his condolences in a tweet today.
Strongly condemn murder of RU amb to TK Andrei Karlov. Condolences to his family. Dynamics&responsibilities of this must be fully clarified— Ex EP President (@EP_PresSchulz) December 19, 2016
In the middle of a question and answer session, Theresa May said: "I was just looking at what I believe ... is some breaking news, that the Russian ambassador to Turkey has been shot, a matter which is yet to be confirmed, but I think is a matter of concern."
US State Department spokesman John Kirby spoke out against the attack in a statement: "We condemn this act of violence, whatever its source. Our thoughts and prayers are with him and his family."
Following the news of the attack, Turkey's lira and Russia's ruble both weakened and US treasuries added to price gains.
The lira was last down about 0.5 per cent at 3.525 lira per US dollar, while the rouble hit a session low of 62.045 rouble per dollar before retracing to 61.800, according to Reuters data.
US treasury yields fell further from multi-year highs, with benchmark 10-year notes last 2.53 per cent, down from 2.55 per cent before the reports and from 2.60 per cent late Friday.