The head of al-Qaeda’s offshoot in Syria has called on followers to carry out retaliatory attacks in Russia, raising the specter of blowback on Russian soil over Moscow’s military intervention to aid Syria’s embattled government.

Just hours after the call from Abu Mohammed al-Jolani, the leader of Jabhat al-Nusra, two mortar shells landed in the perimeter of the Russian Embassy in the Syrian capital, Damascus. No casualties were reported.