Russian President Vladimir Putin says his security forces will track down those behind the assasination of the country's ambassador to Turkey.
Andrei Karlov was shot dead as he was giving a speech at an arts centre in Ankara.
Turkish security sources say the gunman was a 22-year-old off-duty police officer who worked in the city.
It is reported he shouted "Don't forget Aleppo" as he carried out the attack.
Foreign Affairs Minister Charlie Flanagan has condemned the assasination.
Russia's President Putin says the killing was an act of terrorism:
