At least 23 people are reportedly dead and many more injured after a large explosion in the rebel-held city of Idlib, in north-western Syria.

The UK-based Syrian Observatory for Human Rights said the blast struck the headquarters of a minor rebel faction.

Seven of the dead are believed to be civilians.

It is unclear what caused the blast in the city’s Thalatheen Street. Some reports suggest it was a car bomb, while others say it was a drone attack.

The Observatory, which monitors Syria’s civil war through a network of sources, said rescue teams were working to recover the dead and wounded from the damaged building and nearby houses.

Several people remain unaccounted for.