Saudi Arabia
A military truck belonging to the Saudi border guards force patrol near a fence on Saudi Arabia's northern borderline with Iraq.Reuters

Saudi Arabia has extended a secure zone on its northern border with Iraq to ward off potential threats, a Saudi official has told Bloomberg.

The world's largest oil supplier widened the buffer zone from 10 to 20 kilometres "due to some threats that may come from the north," Saudi Border Guard spokesman Muhamad al-Ghamdi told Bloomberg.

"That is why we added 10 kilometres to the buffer zone. This will help the border guards perform their mission."

Border guards "called on residents and citizens to stay away from the border areas," the Saudi Press Agency said in a statement.

Saudi forces are part of the US-led coalition conducting airstrikes in Iraq and Syria against targets from the so-called Islamic State, whose self-declared caliphate spans parts of both counties.

Although most of the fighting in Iraq has taken place in the north of that country, the leadership in Riyadh is concerned that the conflict in its neighbour could spill over the border into Saudi territory.

Both Sunni jihadists and the Shia militias fighting in the Iraqi and Syrian wars pose a threat to the kingdom.

Hundreds of Saudi citizens are thought to have travelled to fight with the Islamic State in Syria and Iraq, while dozens have reportedly blown themselves up in suicide bombing attacks in the war.

Southern Threat

Meanwhile, Riyadh has also tightened security around its southern border with Yemen, where the Shia rebel Houthi group has waged an insurgency in recent months.

The Houthis are widely thought to receive financial and military support from Iran, Saudi Arabia's main regional rival. The Saudis have long claimed that Tehran uses the movement undermine stability in Yemen and pose a security threat close to its borders.