Beirut (AFP) - Lebanon's Hezbollah movement on Saturday accused US-led forces of stranding a convoy of Islamic State fighters and civilians headed for Syria's Deir Ezzor province under an evacuation deal.

The convoy carrying hundreds of IS fighters as well as civilians was meant to travel from the Lebanon-Syria border to jihadist-held territory in eastern Syria under a deal Hezbollah helped broker.

But the US-led coalition has pounded the road to Deir Ezzor with air strikes to prevent the convoy reaching the IS-held town of Albukamal on the Iraqi border.

Hezbollah, which has defended the deal to remove IS fighters from the Lebanese frontier, said US-led forces had effectively stranded most of the convoy's 17 buses in the Syrian desert, beyond government reach.

"They are also preventing anyone from reaching them even to provide humanitarian assistance to families, the sick and wounded and the elderly," the Hezbollah statement said.

The convoy left the Lebanon-Syria border region on Monday, but Hezbollah said six of the buses remained in Syrian government-held territory.

The deal, brokered by Hezbollah with the support of its Syrian regime ally after a week-long offensive against IS, has been fiercely criticised by US-led forces and the Iraqi government.

The international coalition fighting IS has said it is unacceptable for jihadists to be transported to the border with Iraq, where pro-government forces this week ousted the extremist group from the northern city of Tal Afar.

In a statement overnight, the coalition said it had sent a message to Damascus through Syria's ally Russia to say that "the Coalition will not condone IS fighters moving further east to the Iraqi border."

"The Coalition values human life and has offered suggestions on a course of action to save the women and children from any further suffering as a result of the Syrian regime's agreement," it added, without providing further details.

The coalition said it would not strike the convoy, but acknowledged hitting IS fighters and vehicles "seeking to facilitate the movement of IS fighters to the border area of our Iraqi partners."

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Hezbollah accused US forces of hypocrisy, saying they had previously allowed IS fighters to flee territories in Iraq.

Iraqi Prime Minister Haider al-Abadi has described the deal as "unacceptable" and an "insult to the Iraqi people".

In Lebanon some criticised it for allowing fighters suspected of killing Lebanese citizens to escape on "air-conditioned buses."

Deir Ezzor in Syria's east is one of the jihadists' last remaining strongholds, where they hold most of the province and parts of its capital of the same name.