Sunni militants led by the Islamic State of Iraq and the Levant took control of an Iraq-Syria border crossing after Syrian rebels withdrew overnight, security officers and witnesses said.

The sources said insurgents took control of the Al-Qaim border crossing, one of three official border points between Iraq and Syria, after gunmen linked to the Free Syrian Army (FSA) and Al-Qaeda-affiliated Al-Nusra Front left.

"Gunmen took full control of Al-Qaim and areas surrounding it," a police lieutenant colonel said, speaking on condition of anonymity.

He said the militants, who include ISIL but also several other armed Sunni groups, did not enter the actual border crossing buildings for fear of booby traps.

An army major confirmed that the town and its surrounding areas were in insurgent hands.

The takeover of Al-Qaim spurred families in the town to flee, according to an Iraqi border guard whose unit is stationed in the town of Rawa, to the east.

Gunmen loyal to the FSA and Al-Nusra Front seized the Iraqi side of the border crossing on June 17 following the withdrawal of security forces and after having already held control of the Syrian side.

A broad militant alliance including ISIL and other groups has overrun a swathe of territory north of Baghdad in less than two weeks, alarming the international community and threatening Iraq's very existence.

After performing poorly during the initial period of the onslaught, the Iraqi security forces appear to have recovered and are fighting to retake territory, with mixed results.'

AFP