A joint investigation is getting underway into the assassination of Russia's ambassador to Turkey.

Ambassador Andrey Karlov was killed by an off-duty police officer while attending an art gallery yesterday, at the opening of a photo exhibition.

There are reports this lunchtime that a number of arrests have been made, although yesterday's assassin was killed in a firefight with special forces.

The assassin shouted "Don't forget Aleppo, don't forget Syria" shortly after carrying out his attack, which has been met with worldwide condemnation.

Russia and Turkey have experienced a complex relationship over Syria - with Russia supporting the forces of President Bashar al-Assad, Turkey backing the opposition Free Syrian Army, but both fighting against the uprising of Islamic State and associated terrorism.

Our political correspondent Gavan Reilly has this report, which contains scenes that some listeners might find distressing.