MOSCOW, December 20 (RAPSI) - A criminal case has been opened into the murder of Russian ambassador to Turkey Andrey Karlov, the Investigative Committee announced on Tuesday.

On Monday evening, an unidentified gunman, allegedly an off-duty police officer, opened fire at an art gallery in Ankara when Karlov was giving a speech. The ambassador was mortally wounded. At least three other persons were reportedly injured.

The gunman was later killed by police officers in a shootout, according to Turkish officials.

Videos of the assassination taken by journalists give investigators a reason to believe that the gunman’s actions and speech were related to his opinion concerning Russia’s policy in combating international terrorism.

Russian President Vladimir Putin said that Karlov had been “despicably killed”. The Turkish President, Recep Tayyip Erdogan, in turn characterized the murder of Russian ambassador as a terrorist attack aimed at deterioration of relations between the countries after the beginning of their normalization.

Relations between Russia and Turkey became troubled in October 2015 after killing Oleg Peshkov, the pilot of Russian Su-24 bomber downed by the Turkish Air Force in Syria. At that time, President Vladimir Putin described the murder of Russian pilot as “a stab in the back delivered by accomplices of the terrorists.” In the fall of 2016, Putin and Erdogan negotiated over getting Russia-Turkey relationship back on track.