"The explosion occurred early this morning at a military facility near the town of Al-Eis", Syria's state news agency SANA reported, referring to the town southwest of Aleppo city, the provincial capital. The cause of the incident remains unknown.

Aleppo's internal security command stated that roads leading to the scene were blocked to ensure public safety. Faisal Mohammad Ali, leader of Aleppo's defense forces, said secondary explosions are hindering rescue teams from reaching the site.

Explosion at a military base in Al-Eis town, Aleppo province, Syria on 21/9. Video: X/sentdefender.

Azzam al-Gharib, governor of Aleppo, advised residents not to leave their homes. "Hospitals, ambulances, and emergency rescue teams are on high alert", he said.

A resident in the Hamadaniyeh district, southwest of Aleppo city, reported hearing "an extremely loud explosion". From a rooftop, the resident saw large flames rising in the distance.

Locations of key cities in Syria. Graphics: AP.

Syria has recently recorded several incidents at military facilities. An explosion of unknown cause occurred on 18/9 at a base in the eastern province of Deir ez-Zor, killing 11 people. On 1/9, an arms depot in the northwestern province of Idlib exploded, killing 14 people and injuring 11.

Nguyen Tien (According to AFP, Al Jazeera, AP)