The US military said a rocket attack late Thursday targeted international coalition forces in northeast Syria, without causing any casualties.

The US-led anti-jihadist coalition maintains bases in areas controlled by Syria's Kurdish forces, including at Al-Omar, the country's largest oil field.

"Rockets targeted coalition forces" at the Green Village base at Al-Omar, which is close to the Iraqi border, the US Central Command said in a statement.

There was no damage to the base or casualties, but such attacks "undermine the hard-won security and stability" of the region, said the statement.

"US forces in northeastern Syria are investigating the incident," it added.

The UK-based Syrian Observatory for Human Rights reported "four rockets were fired from a pro-Iranian militia base in the Mayadine region", close to the coalition forces.

"Both parties put their forces on alert" after the attack, added the Observatory.

Pro-Iranian militia hold significant influence in Syria's border area with Iraq, an important crossing point for weapons, fighters and goods.

On November 9, a convoy of weapons and fuel destined for pro-Iranian militias in Syria was targeted in an airstrike near the Iraqi border, killing at least 14 people according to the Observatory.

The US and its coalition allies denied carrying out the attack, while Israel, which regularly conducts operations against Syrian and pro-Iranian forces in the country, declined to comment.