At least 40 of them were killed in a rocket attack on a meeting of leaders of radical jihadist groups near the northern Syrian city of Idlib on Saturday, the Syrian Observatory for Human Rights said.
The director of the observatory Rami Abdel Rahman told AFP that "missile strikes targeted a meeting held by leaders of the factions of the guards of religion and Ansar al-Tawhid and allied groups inside their training camp" near the city of Idlib, causing the death of "at least 40 of them."
The al-Qaida-linked Haras al-Din faction and al-Tawhid supporters are active in and around Idlib, where they join a joint operations room with other militant factions. These factions are fighting alongside HTS (formerly Jabhat al-Nusra).
An AFP correspondent saw plumes of black smoke rising from farms north of the city of Idlib, after successive explosions echoed in the area.
Ambulances rushed to the targeted location, which journalists could not approach, he said.
The observatory was unable to determine "whether the planes carried out these strikes or were the result of long-range missile shelling," as the ceasefire in Moscow and Damascus has been in effect since Saturday morning has been approved by Damascus.
The Haras al-Din faction was founded in February 2018 and includes about 1,800 fighters, including non-Syrian nationalities, according to the Observatory.
In early July, Washington confirmed a raid against the al-Qaeda leadership in Syria, targeting a training camp in the northern province of Aleppo.
"The operation targeted members of al-Qaeda in Syria responsible for planning external attacks that threaten American citizens, our partners and innocent civilians," the US Central Command said in a statement.
The raid, according to the observatory, killed eight elements, including six leaders of different nationalities of the Arab organization of the Guardians of religion.
US forces leading the international coalition against ISIS have repeatedly targeted jihadi leaders in the Idlib area. Since 2017, however, the pace has fallen sharply, with strikes focused on areas controlled by the jihadist group.
