Explosives brought down the Russian-operated Airbus A321 over the Sinai, Russiaâ€™s federal security service chief has told president Vladimir Putin.
FSB director Alexander Bortnikov met with Putin and other senior government figures on 16 November, the presidentâ€™s office states.
Bortnikov told Putin that personal belonging, baggage and debris from the MetroJet A321 had been studied by investigators.
These examinations have â€œrevealed traces of foreign-produced explosiveâ€, he stated.
The aircraft was transporting an improvised device, with an explosive capacity of up to 1kg of TNT, said Bortnikov, leading to its destruction in the air.
â€œYou can definitely say that this is an act of terrorism,â€ he added.
None of the 224 occupants of the aircraft, which departed Sharm el-Sheikh bound for St Petersburg on 31 October, survived.
Putin responded by stating that the attack was â€œnot the first timeâ€ the country had faced such acts, noting the rail station bombing in Volgograd at the end of 2013.
He vowed that Russiaâ€™s military aviation operations in Syria would be â€œstrengthenedâ€, so that perpetrators of such attacks would â€œrealise that retribution is inevitableâ€.
â€œWe will look for them wherever they might be hiding,â€ he said. â€œWe will find them anywhere in the world, and punish them.â€