(Adds comment from Saudi security spokesman)
DUBAI, July 3 (Reuters) - Saudi-owned al-Arabiya television said Saudi Arabia had deployed 30,000 soldiers to its border with Iraq on Thursday after Iraqi forces abandoned the area, but Baghdad denied pulling forces back and said it remained in full control of its frontier.
Saudi Arabia, the world's top oil exporter, shares an 800-km (500-mile) desert border with Iraq, where Islamic State insurgents and other Sunni Muslim militant groups seized towns and cities in a lightning advance last month.
The U.S.-allied kingdom overcame its own al Qaeda insurgency almost a decade ago and is wary of any new threat from radical Sunni Islamists.
The Dubai-based al-Arabiya said on its website that Saudi troops had fanned out into the border region after Iraqi government forces withdrew from their positions, leaving the Saudi and Syrian frontiers exposed.
It aired a video which, it said, showed some 2,500 Iraqi soldiers in the desert region east of the Iraqi city of Kerbala after pulling back from the border, which is reinforced on the Saudi side by a system of fences.
An officer in the video said that the soldiers had been ordered to quit their posts without justification. The authenticity of the recording could not immediately be verified.
However, the Iraqi prime minister's military spokesman, Lieutenant General Qassim Atta, told reporters in Baghdad: "This is false news aimed at affecting the morale of our people and the morale of our heroic fighters."
He said the frontier, which runs through largely empty desert, was "fully in the grip" of Iraqi border troops.
Saudi Arabia's Interior Ministry security spokesman, Major General Mansour Turki, said: "We have not experienced any insecurity close to our border, and our border is secured and protected long before the latest events in Iraq."
The state news agency SPA said King Abdullah had ordered all necessary measures to protect the kingdom against potential "terrorist threats".
Diplomatic sources in the Gulf say Saudi Arabia's border with Iraq is relatively well defended, but that its frontier with Jordan might provide an easier route for any militants trying to enter Saudi Arabia from Iraq.
(Reporting by Sami Aboudi; Editing by Kevin Liffey)