The plane which crashed over Egypt killing all 224 Russians on board was a terror attack, the Kremlin has confirmed.
Russia's Federal Security Service said last week they were 90% sure it was caused by a bomb and revealed explosives had been found in the debris.
But the country has now said for the first time it was "unequivocally a terrorist act".
President Vladimir Putin has vowed to find those responsible for the October 31 crash and ordered special services to investigate.
He also said Russia would now step up its air strikes against Syria.
Meanwhile, it has emerged Tunisia stopped a major terror attack planned this month against hotels and police stations, according to government officials.