The Syrian army and its allies have secured the Palmyra to Deir al-Zor road, a major supply route from government territory to the eastern city, defeating a strong Islamic State attack, a military media unit run by Lebanon's Hezbollah said on Friday.

Islamic State's assault, which began on Thursday, marks the first major counterattack against the Syrian army and its allies since they broke through a swathe of territory to reach the city of Deir al-Zor earlier this month.

Hezbollah is one of the main allies of Syrian President Bashar al-Assad, alongside Russia, Iran and other Shi'ite militias.

Earlier on Friday, a commander in the military alliance backing Assad said the road linking Deir al-Zor to Palmyra was only being used in cases of absolute necessity and that the army and its allies were fighting to recover lost ground.

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