A Turkish policeman has assassinated Russia's ambassador to Turkey, shouting “Don’t forget Aleppo, don’t forget Syria”, before being killed himself.

Mevlut Mert Altintas, reported to be an off-duty policeman,  shot Ambassador Andrey Karlov at around 19:05 local time on December 19 while Karlov was giving a speech at the opening ceremony of a photo exhibition in the Turkish capital, Ankara. 

Karlov did not respond to emergency treatment at hospital and was declared dead at around 19:53 local time, according to Turkish Interior Minister Suleyman Soylu.

The gunman was wearing a dark suit of a type typical of a security detail. A video that appeared on Twitter showed Altintas standing behind Karlov at the event as if he was part of the security team, and then shooting him in the back at close range, before haranguing onlookers.

As is usual the Turkish authorities quickly imposed a media blackout on the story, as it does with all terror attacks. Turkish officials said later they were investigating possible links between the gunman and US-based Islam cleric Fethullah Gulen, whom Ankara blames for the attempted military coup in July.

The attack comes after Russia and Turkey had rebuilt bilaterals relations after Ankara's shooting down of a Russian bomber near the Syrian border last year. Nevertheless relations remain strained because of Russia's support for Syrian President Bashar al-Assad – notably in the reconquest of Aleppo from rebel forces – while Turkey has backed the opposition.

Turkish President Recep Tayyip Erdogan said on TV that he had had a telephone call with his Russian counterpart Vladimir Putin to express his sympathy and that the two countries would set up a joint investigative committee.

Russia views the assassination as a terrorist act and will raise the matter at a UN Security Council meeting, the Russian Foreign Ministry said.

The US Department of State and EU foreign policy chief Federica Mogherini also condemned the attack.

Turkish, Russian and Iranian foreign ministers were expected to hold talks on Syria at a meeting to be held on December 20 in Moscow. Turkish Foreign Minister Mevlut Cavusoglu is currently in Moscow and the Turkish Defence Minister was planning to leave to join him, Soylu said.