A Turkish policeman crying "Aleppo" and "Allahu Akbar" shot dead Russia's ambassador to Turkey in Ankara on Monday, prompting a vow from President Vladimir Putin to step up the fight against "terrorism."

Andrei Karlov died of his wounds after the shooting in an Ankara exhibition center, which came on the eve of a key meeting in Moscow between the Russian, Turkish and Iranian foreign ministers on the Syria conflict.

Dramatic footage showed the moment the gunman shot the veteran diplomat in the back as he opened a show of Russian photographs.

Images showed the ambassador standing up to speak at a lectern, before stumbling and crashing to the ground as shots ring out, lying flat on his back as the attacker -- dressed in a dark suit, white shirt and tie -- brandishes his gun at shocked onlookers.

The man shouts "Allahu Akbar" ("God is greatest") and then talks about pledging allegiance to jihad in Arabic, the images showed.

Switching to Turkish, he then says: "Don't forget about Syria, don't forget about Aleppo. All those who participate in this tyranny will be held accountable".

The state-run Anadolu news agency said the gunman had been "neutralised" in a police operation inside the hall after 15 minutes of clashes when he refused to surrender.

Turkish Interior Minister Suleyman Soylu identified the attacker as Mevlut Mert Altintas, 22, who had worked in the Ankara anti-riot police for the last two and a half years.

His mother, father and sister were reportedly detained for questioning in their home in western Turkey.