TAKING CREDIT: ISIS Celebrates St. Petersburg Metro Blast That Killed 10.

“We ask Allah to bless the operation by the lions of the Caliphate, we ask Allah to kill the Crusaders,” said an ISIS supporter from the terror group’s al-Minbar online forum. Others celebrated by saying that the Monday bombs made for “a metro to hell for the worshipers of the Cross” and claimed that the attacks — which are still under investigation by Russian authorities — were revenge for Russia’s backing of Syrian President Bashar al-Assad, who is fighting against ISIS and other rebel groups in a six-year-long civil war. Russian airstrikes and shelling in Syria have killed hundreds of people and reduced entire areas to rubble.

If Moscow accepts ISIS as the culprits, the aftermath could prove the first real test of Russia’s renewed position in the Middle East.