Washington — The United States has deployed mobile artillery rocket launchers in southern Syria, aiming to defend its At-Tanaf base where it trains anti-Islamic State forces, Pentagon officials confirmed Thursday.

Officials would not say how many of the HIMARS units, a truck-mounted multiple rocket launch system, had been moved into the area.

But the deployment came after forces backing the regime of Syrian President Bashar al-Assad moved into an established "de-confliction" zone close to the At-Tanaf garrison inside the southern Syria border weeks ago, creating a new threat.

The move sparked a protest from Russia, which supports Assad and said the HIMARS system would be used against Syrian government forces.

"Deploying any type of foreign weapons on Syrian territory... must be approved by the government of the sovereign country," Russia’s defense ministry said.

"Forces of the US-led anti-IS coalition have repeatedly issued strikes on Syrian government forces fighting IS near the Jordanian border."

"It’s not hard to guess that similar strikes will be continued against contingents of the Syrian army in the future using HIMARS," it said.

The HIMARS system has already been deployed before in Iraq and Syria against the Islamic State group.

It gives US forces a precision attack ability even in poor weather when air attacks are hindered.

It can launch six guided rockets that have than 70 kilometer (37 mile) ranges, or a single missile with a 300 kilometer range.

On June 6 the US-led coalition said it had destroyed a unit of pro-regime forces in Syria on Tuesday as they advanced near at-Tanaf.

And one week ago a drone thought to be controlled by pro-regime forces fired on coalition troops in the area before it was shot down.—AFP