"We shouldn't rush with any theories before the investigators establish who were behind the assassination of our ambassador," said spokesman Dmitry Peskov - though he offered no theories about who the culprits might be.

The ambassador, Andrei Karlov, was shot dead on Monday evening in front of stunned onlookers at a photo exhibition in Ankara. His assassin, Mevlut Mert Altintas of Ankara's riot police squad, was subsequently killed in a police operation.

On Tuesday, Russia flew a team of 18 investigators and foreign ministry officials to Turkey to take part in the probe.

Their plane returned with Mr Karlov's body. Russian officials and Turkish foreign minister Mevlut Cavusoglu who was visiting Moscow met the family at the Vnukovo airport late on Tuesday.

Ankara has not made public any theories, but a senior Turkish government official said on Tuesday it was unlikely Altintas acted alone.

The official said the killing had all the marks of being "fully professional, not a one-man action".

Mr Peskov told reporters that Moscow will wait for the investigation to conclude before voicing any theories.

Earlier on Wednesday, the Russian State Duma voted on a resolution which urged authorities to take extra steps to protect Russian diplomats abroad.