Syrian opposition groups lobbed hundreds of missiles and artillery rockets at government posts in northwestern Syria on Tuesday, in retaliation for a deadly attack that killed dozens of their fighters a day earlier. The Turkey-backed groups, operating under the umbrella of the National Front for Liberation, fired hundreds of artillery rounds and missiles since late Monday at government posts in territories adjacent to areas they control in Idlib and Aleppo provinces. A spokesman for the NFL, Naji al-Mustafa, said the rebel’s military retaliation targeted and killed Russian officers in southern Idlib, as well as Syrian soldiers working in the area.