ANKARA -- Russia's Ambassador to Turkey Andrey Karlov was shot and killed on Monday at an art exhibition in the Turkish capital of Ankara.

The gunman, who shouted "Don't forget Aleppo," was identified as a Turkish off-duty police officer, according to Turkish security sources.

The Yeni Safak daily said on its website that the attacker, named as M.M.A., worked with anti-riot police in Ankara.

Karlov was shot in the back while making a speech at a painting exhibition in the Turkish capital, the Russian embassy said.

Three other wounded people were taken to Guven Hospital in central Ankara.

Witnesses said attendants at the exhibit ran away after the attacker opened fire.

The Russian Foreign Ministry has confirmed that the ambassador was killed in the attack.

The attack came one day before Turkish Foreign Minister Mevlut Cavusoglu heads to Moscow for talks on Syria with his Russian and Iranian counterparts.