DAMASCUS - At least 39 people, including 21 children and women, were killed on Sunday when an explosion rocked the rebel-held town of Sarmada in northern Syria near the Turkish border, a monitor reported.

The explosion took place in an ammunition depot belonging to the al-Qaida-linked Nusra Front, otherwise known as the Levant Liberation Committee (LLC), according to the Syrian Observatory for Human Rights.

The depot was located on the bottom floor of a residential building, which was completely destroyed during the explosion, the London-based watchdog said.

Many people were buried under the rubble, most of whom were displaced people from the central province of Homs, it added.

The death toll could further rise given a large number of the critically wounded and those still trapped under the rubble.

In a separate incident on Sunday, a roadside bomb went off as a bus was passing by in the rebel-held town of Twaineh in the countryside of Hama Province in central Syria, leading to 14 injuries.