The extremist movement Hayat Tahrir al-Sham (HTS) carried out a surprise attack on the Syrian army in Aleppo province on Wednesday.
Then, both the Syrian and Russian air forces attacked HTS members in the area, for the first time in several years, according to the London-based Syrian Human Rights Observatory (SOHR).
At least 57 people were killed on both sides, reports SOHR. HTS, an extremist movement spawned from al-Qaeda, controls parts of the Idlib province.
