A huge blast killed at least 11 civilians as it wrecked a multi-storey building in Syria’s northwestern jihadist-held city of Idlib on Monday, a war monitor said.

A huge blast killed at least 11 civilians as it wrecked a multi-storey building in Syria’s northwestern jihadist-held city of Idlib on Monday, a war monitor said, South China Morning Post reported.

The group, which relies on sources inside Syria for its information, said the death toll was likely to rise as several of the wounded were in serious condition and many others were trapped under the rubble.

The cause of the explosion was not immediately clear. An AFP correspondent at the scene saw volunteers operate a bulldozer in the dark near the collapsed multi-storey building, as rescuers searched for victims using lamps.

Idlib city is controlled by Hayat Tahrir al-Sham, a group led by Syria’s former al-Qaeda affiliate. Held by an array of jihadists and rebels, the surrounding province of the same name is the last in Syria largely beyond government control.

More than 350,000 people have been killed in Syria’s seven-year civil war since it started in 2011 with the brutal repression of anti-government protests.