Iraqi military officials have denied that troops have abandoned positions along the border with Saudi Arabia. Interior ministry spokesman Brig Gen Saad Maan said the country's border force was functioning normally, BBC News reported.

Earlier, al-Arabiya TV reported that Saudi Arabia had deployed 30,000 soldiers along the 900km (560-mile) frontier after Iraqi forces withdrew. The Saudi personnel were fanning out along the border to prevent attacks by jihadist-led Sunni rebels, it said.

Last week, King Abdullah ordered all necessary measures to be taken to protect Saudi Arabia against "terrorist threats".

On Wednesday, July 2, he discussed Iraq and the threat posed by the Islamic State in Iraq and the Levant (Isis) with US President Barack Obama.

Obama also thanked the Saudi monarch for his $500m donation to the United Nations to help it address the humanitarian crisis caused by the insurgency in Iraq.

More than one million Iraqis have fled their homes over the month as Sunni rebels led by Isis overran Mosul, Tikrit and other cities and towns in the north and west. At least 2,461 people were killed in violent attacks in June, according to the UN and Iraqi authorities.