Blast in northwest Syria kills four

A blast that rocked Syria's northwestern Idlib province on Thursday killed four people, state media said, though the cause had yet to be officially determined.

Residents told AFP they heard the sound of explosions on the western outskirts of the provincial capital, with a war monitor saying they came from a nearby base for foreign fighters.

State news agency SANA reported "an explosion whose cause is unknown in the vicinity of the city of Idlib".

Citing the health ministry, it reported at least "four dead and five others injured", raising an earlier toll of two dead.

The civil defense said in a statement that a child was among those killed.

The Syrian Observatory for Human Rights reported "the sound of successive large explosions at a base for non-Syrian fighters containing a weapons depot as a drone was in the air".

The Britain-based monitoring group reported thick smoke and panic among residents of the area.

Late last month, a series of explosions in Idlib province killed at least 12 people and wounded more than 100, the Observatory said at the time.

Those blasts occurred at a weapons depot belonging to Uyghur jihadist group the Turkistan Islamic Party (TIP) in Maaret Misrin, the monitor reported.

Authorities did not immediately say what may have caused those explosions.