The militants, led by the Islamic State in Iraq and Levant (ISIL), first moved into the nearby town of al-Qaim on Friday, pushing out security forces, the sources said.
Once the border guards heard that al-Qaim had fallen, they left their posts and the militants moved in, the sources said.
However, the media adviser to the commander of Iraq’s anti-terrorist squad told Reuters that the Iraqi army was still in control of al-Qaim.
With stunning speed, ISIL has captured swathes of territory in northwest and central Iraq, including the second city, Mosul. They have seized large amounts of weaponry from the fleeing Iraqi army and looted banks.
Al-Qaim and its neighboring Syrian counterpart Albukamal are on a strategic supply route. The Albukamal gate is run by al Qaeda’s official Syria branch, the Nusra Front, which has clashed with ISIL but has also agreed to localised truces when it suits both sides.