President Vladimir Putin has vowed to hunt down those responsible for blowing up a Russian airliner over Egypt and intensified air strikes against militants in Syria, after the Kremlin concluded a bomb had destroyed the plane last month, killing 224 people.

Mr Putin ordered the Russian navy in the eastern Mediterranean to coordinate its actions on the sea and in the air with the French navy, after the Kremlin used long-range bombers and cruise missiles in Syria and announced it would expand its strike force by 37 planes.

“We will find them anywhere on the planet and punish them,” Mr Putin said of the plane bombers at a sombre Kremlin meeting broadcast yesterday. Until yesterday, Russia had played down assertions from Western countries that the Ocober 31 crash was the work of terrorists, saying it was important to let the official investigation run its course.

But four days after Islamist gunmen and bombers killed at least 129 people in Paris, Alexander Bortnikov, the head of the FSB, said in televised comments that traces of foreign-made explosive had been found on fragments of the downed plane and on passengers’ personal belongings.

“We can unequivocally say it was a terrorist act,” Mr Bortnikov said at a Kremlin meeting.

Egyptian authorities have detained two employees of Sharm al-Sheikh airport, where the plane originated, for questioning.