AMMAN- An explosion at a training camp for jihadist fighters in opposition-held northwest Syria killed at least 10 people and injured a dozen other recruits, residents and opposition sources said.

The explosion took place while dozens of fighters from the Hyat Tahrir al Sham (HTS) group were attending a training session on artillery and mortars in the camp near the town of Hasano, in northern Idlib province, two military opposition sources told Reuters.

"There was a mistake which led to an explosion during a training session on mortars," said Mohamad Rasheed, an opposition activist familiar with the details of the incident.

HTS is a jihadist group that controls parts of Syria’s northwest, a rebel-held area still at war with Damascus. Formerly known as the Nusra Front, it has been designated a terrorist group by the United States, Turkey and others.

(Reporting by Suleiman Al-Khalidi; Editing by Giles Elgood) ((suleiman.al-khalidi@thomsonreuters.com; +96279-5521407;))