"It rather looks like a chain of tragic accidental circumstances," Putin told reporters, rejecting any comparisons with the downing of a Russian jet by Turkey in 2015.

"An Israeli jet did not shoot down our plane," Putin said.

The Russian defence ministry earlier Tuesday blamed Israel for the accident and warned of reprisals.

Putin said he had signed off on the defence ministry statement.

"No doubt we should seriously look into this," Putin said, speaking at a news conference after talks with Hungarian Prime Minister Viktor Orban.

Moscow would beef up security for Russian military personnel in Syria as a priority response, Putin said.

"These will be the steps that everyone will notice," he said, without providing further details.

He expressed condolences to the families of the victims, calling the accident a "tragedy for us all."

Late Monday Syria accidentally shot down the Russian plane, killing all 15 crew members, when its air defences swung into action against an Israeli strike.

The incident was the worst case of friendly fire between the two allies since Russia's game-changing military intervention in September 2015.

The Russian plane was downed by a Russian-made S-200 air defence supplied to Syria.

The Russian Ilyushin dropped off the radar over the Mediterranean soon after Turkey and Russia announced a deal that offered millions of people reprieve from a threatened military assault in northern Syria.