Russia’s security chief says that it was an act of terror brought down the Russian A321 airliner in Egypt last month, killing all 224 people on board.
“Traces of foreign explosives” were found on debris from the Airbus plane, FSB chief Alexander Bortnikov told Russian President Vladimir Putin.
Mr Putin vowed to “find and punish” those behind the attack over the Sinai peninsula. A branch of Daesh said it downed the plane.
Nearly all the dead were Russians.
Mr Bortnikov said a bomb had been planted on board the Metrojet plane, equivalent to up to 1kg of TNT.
The bomb shattered the plane mid-air on 31 October, he said, “which explains the wide dispersal of fuselage pieces”.
Russia has offered a $50m (Â£33m) reward for information on the Sinai plane attackers.
Sinai Province, a branch of Daesh, said in a statement on 31 October that it had destroyed the plane because of Russian air strikes in Syria.
Most of the A321 passengers were Russian tourists flying home from the Red Sea resort of Sharm el-Sheikh.