"US planes fired two guided missiles at a fixed position of Hashed al-Shaabi units on the border with Syria, killing 22 fighters and wounding 12," said the Iran-backed Hashed (Popular Mobilisation Units).

It said the raid took place "700 metres (yards) inside Syria".

The Syrian Observatory for Human Rights said earlier that more than 50 fighters allied to the Damascus regime, most of them foreign, were killed in Sunday night's raid on Al-Hari in eastern Syria.

Syrian state media, citing a military source, accused the US-led coalition fighting the Islamic State jihadist group of having carried out the raid.

Several people were killed and wounded, state media said, without giving precise figures.

The coalition's press office said it had heard reports that a strike in the area of Al-Hari had killed and wounded members of a pro-regime Iraqi group, but denied it was responsible.