Russian authorities have confirmed a bomb brought down a passenger plane over the Sinai Penininsula in Egypt last month, killing all 224 people on board. The self-proclaimed Islamic State had claimed responsibility for taking down the plane, calling it retaliation for Russia’s airstrikes in Syria. Russian officials say an examination of the wreckage confirms an “improvised explosive device” went off soon after the plane departed Sharm el-Sheikh en route to St. Petersburg. Russian President Vladimir Putin vowed to intensify Russian airstrikes in Syria in response to the bombing.

Russian President Vladimir Putin: “The murder of our people in Sinai is one of the bloodiest by the number of victims of such crimes. We won’t wipe off tears over our hearts and souls. It will stay with us forever. But that will not prevent us from finding and punishing the perpetrators.”