Updated

The military chief of Syria's main Western-backed rebel group is warning that the country risks a "humanitarian disaster" if allies do not send more aid to help his moderate forces stop advancing Islamic militants.

Brig. Gen. Abdul-Ilah al-Bashir, commander of the Free Syrian army, said in a statement Saturday that fighters of the extremist Islamic State group were systematically seizing areas held by rival factions.

His plea comes as fierce infighting among the Islamic extremists and moderate rebels has overshadowed their battle against President Bashar Assad.

Al-Bashir called on the United States and other allies to speedily send weapons and ammunition.

Extremist Sunni militants have seized swaths of northern and western Iraq and are advancing along the border in Syria as well.