The United States said Wednesday that Russia's air war in Syria had "dangerously exacerbated" the conflict, accusing Moscow of seeking to bolster President Bashar al-Assad's regime instead of targeting jihadists.

Washington's latest broadside against Russian intervention in Syria came as government troops, emboldened by Moscow's support over the past month, recaptured from the "Islamic State" (ISIS) terrorist group a key road into second city Aleppo, AFP reports.