Nine top Syrian rebels fighting to overthrow President Bashar Assad resigned Saturday citing shortages and mismanagement of foreign military aid.

Lieutenant-Colonel Mohammad Abboud told Agence France Presse he and eight other officers quit because there was "too little" military aid from donor countries, including Western supporters of the revolt.

And they said the rebels' Supreme Military Council (SMC) of which they were key members, "has no role anymore. Donor countries have completely bypassed it".

Their resignation comes more than three years into the anti-Assad revolt, which saw protesters take up arms against the regime after the authorities unleashed a brutal crackdown against dissent.

Weapons shipped to Syria from the West, but far more significantly from Gulf countries, are usually sent to specific groups, rather than to the Supreme Military Council, which was meant to centralize and coordinate the rebel military effort.

In recent weeks, some Western military aid has trickled into Syria, but overall the United States has been reticent to arm the rebels over fears advanced weapons could end up in jihadist hands.

"While we thank donor countries for their assistance, it has been really insufficient, and simply too little to win the fight," Abboud said.

Abboud also said donor countries have "bypassed" the SMC. Instead, they have funneled military aid, including U.S.-made anti-tank missiles, to factions of their choosing.

Rebels fighting Assad's regime have repeatedly urged the West to give them specialized weaponry to help tip the balance in the war against Assad's forces, which is backed by Iran, Russia and Hizbullah.

Earlier in June, President Barack Obama said Washington would "ramp up" support for rebels, without specifying what kind of aid they would receive.

But, faced with successive military defeats around Homs and Damascus province, rebels say they lack the aid needed to change the course of the war.

"We are fighting both the army and the Islamic State of Iraq and the Levant," Abboud said, referring to a jihadist group operating in Syria and Iraq that Syria's opposition turned against in January.

"Yet we haven't got the help we need from countries who say they support our demands for democracy and a civil state."

ISIL has been battling a range of other rebel groups, from moderates like the FSA to Syrian al-Qaida affiliate Al-Nusra Front, since January.

The inter-rebel fighting is estimated to have killed 6,000 people since then.

On Monday, ISIL fighters in Iraq spearheaded a major offensive in Iraq, seizing swathes of territory in predominantly Sunni areas and pushing towards Baghdad.