Russia has stepped up its attacks on Islamic State (IS) targets in Syria, dispatching long-range bombers and firing a volley of cruise missiles.
The strikes follow a statement by Russia's security chief that a bomb brought down a Russian airliner over Egypt last month, killing 224. Sinai Province, an IS-linked Egyptian group, said it had downed the jet.
Russian officials say the country's air force has flown 2,300 missions over Syria in the past 48 days.
In response to Friday's terror attacks in Paris, which killed 129 people and wounded a further 352, Russian warships have been ordered to work "as allies" with their French counterparts in the Mediterranean.
Speaking at a security meeting held on Monday night, Russian President Vladimir Putin said the country's air campaign in Syria would intensify.
"The combat work of our aviation in Syria should not only be continued, but it should be intensified to make the criminals understand that vengeance is imminent," he said.
This is the second time that Russia has fired sea-launched cruise missiles at targets in Syria.
Last month warships in the Caspian Sea were used, but this time - for the first time - the missiles came from a Russian submarine in the Mediterranean. The targets according to the Russian Ministry of Defence were IS training bases, headquarters and ammunition depots near Raqqa.
Russia is also using "long-range" Tupolev bombers to reinforce its air campaign, many of them launching stand-off cruise missiles.
France too is stepping up its air operations against IS, and when the French aircraft carrier, the Charles de Gulle arrives on station, Paris will have over 30 aircraft at its disposal.
In the wake of the downing of the Russian airliner and the terrible events in Paris, a de facto alliance is emerging to intensify the air campaign against IS.
Sinai Province said in a statement that the attack on the Metrojet airliner was a response to Russian air strikes that had killed "hundreds of Muslims" in Syria.
On Tuesday, FSB chief Alexander Bortnikov said that "traces of foreign explosives" were found on the wreckage of the plane. Mr Putin vowed to "find and punish" those behind the attack.
As well as targeting IS, Russian warplanes are supporting Syrian government forces against various rebel groups - a source of tension between Mr Putin and his US and UK counterparts.
France has also vowed to intensify air strikes against IS after Friday's attacks in Paris were linked to the group. At least 129 people were killed in several co-ordinated attacks in the city and a further 352 injured.
Both Russian and US officials have said they will coordinate closely with France to target IS in the wake of the attacks in Paris.