The Kremlin has said for the first time that it was a bomb that ripped apart a Russian passenger jet over Egypt last month.
President Putin promised to hunt down those responsible and intensify its air strikes on Islamist militants in Syria in response.
Lorna Shaddick reports from Moscow.
IN: One kilogram of..,
OUT: SOC
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1 kilogram of TNT. That's what caused the carnage in the Sinai, according to the Kremlin, which had at first played down assertions from Western countries that the 224 people on board the downed Russian Metrojet plane were killed by terrorists. The head of Russia's security services told Vladimir Putin at a late night Kremlin meeting that traces of explosives were found on passengers' belongings and bits of the fuselage. The President now vows to get tough:
SOT - Super: Vladimir Putin, Russian President
We will search for them everywhere - wherever they are hiding. We will find them in any spot on the planet and punish them. // Our aviation's combat operation in Syria should not just continue. It should be strengthened so the perpetrators will understand that retribution is inevitable.
Outside Moscow's central Mosque, many Russians - Muslim and not - agree that the airstrikes are needed:
VOX - Ibrahim
If Russia doesn't do it, people will have a taste of it here, and I don't wish that on anyone.
VOX - Alexander
If they feel our force, they'll stop carrying out acts of terror. There will be no one left to carry out terror attacks.
On Tuesday President Putin also wanted to emphasise Russia's experience in dealing with terror:
SOT - Super: Vladimir Putin, Russian President
This isn't the first time that Russia faces barbaric terrorist attacks without any obvious reasons, internal or external, like the blast at the railway station in Volgograd in 2013. We have not forgotten anyone or anything.
Expert Mikhail Troitsky says the timing of the revelation wasn't an accident:
SOT - Super: Mikhail Troitsky
I think the announcement of course was calculated politically. That sort of sets Russia together in a coalition of victims of terror, but that's really true. Both Russia and France and Turkey, that all puts them together in one group of victims of ISIS attacks. So it's natural that they eventually reach the conclusion about the sources of those attacks and the causes of the plane crash.
As President Hollande of France prepares to visit Moscow next week, the Russian message is clear - we too are victims of terror, but we're fighting back - and you should join us. Lorna Shaddick, Moscow.