Moscow, Dec 20  Russia has acknowledged the words of support pouring in from various nations in the wake of the assassination of Ambassador Andrey Karlov in Turkey, the Russian Foreign Ministry said on Tuesday.

"We express our appreciation to all our colleagues and partners for their words of support. We highly appreciate the solidarity shown to us," the ministry said in a statement. 

The ministry also said it considered the attack an act of terror, Sputnik news reported.

Karlov was shot by a gunman at an art gallery exhibition opening in Ankara late on Monday. Doctors announced the ambassador's death 40 minutes after his hospitalisation. 

The gunman in a black suit and tie shot dead the Russian Ambassador to Turkey as he was speaking at the opening of a photographic art exhibition in the capital city of Ankara, titled "Russia through Turks' eyes."

The gunman shouted "Don't forget Aleppo. Don't forget Syria. As long as our brothers are not safe, you will not enjoy safety. Whoever has a share in this oppression will pay for it one-by-one. Only death will take me away from here," according to Turkish security sources.

The gunman was shot dead at the scene and identified as 22-year-old Turkish police officer Mevlut Mert Altintas, according to Turkish Interior Minister Suleyman Soylu.

He had been on duty for two and a half years with the riot police unit in Ankara.

Three injured people were taken to Guven Hospital in central Ankara for treatment.

Moscow and Ankara were in the process of normalising ties after the latter shot down a Russian warplane on November 24, 2015 claiming airspace violation.