Syrian armed groups have launched a large-scale attack on areas controlled by government forces, setting off fierce clashes for a second day and seizing territory in Western Aleppo, government and opposition factions said on Thursday.

Syria’s armed forces said on Thursday the offensive was led by Hayat Tahrir al-Sham, or HTS, which controls much of northwest Syria and is a violation of a de-escalation agreement. It said the attacks are ongoing and have targeted a number of villages and military bases.