Almost all the Syrians who fled to the border with Jordan from an army offensive have now returned to their homes, a top UN official says.

Anders Pedersen, the UN humanitarian co-ordinator in Jordan, said that "around 150 to 200 people (are) right now at the border".

The offensive in Syria's south-west had earlier forced more than 320,000 people to flee in recent weeks, the UN says.

Many are now returning after a recent deal between the army and rebels.

The provinces of Deraa and Quneitra had been relatively calm for almost a year because of a "de-escalation" agreement brokered by the US and Jordan, which support the opposition, and Russia, a key ally of the government Syrian President Bashar al-Assad.

However, Mr Assad set his sights on retaking them after defeating rebels in the Eastern Ghouta region outside the capital Damascus in April.

UN war crimes investigators have accused Syria and Russia of systematically bombing medical facilities, which are protected under international law, and intentionally attacking medical personnel, most recently in the Eastern Ghouta.

Both Damascus and Moscow have repeatedly denied the accusations.