The head of Lebanese Shiite movement Hezbollah, who has lived in hiding for the past decade, said Thursday he travelled to Damascus to seek the Syrian president's approval of a jihadist evacuation deal.

"I personally went to Damascus" to see President Bashar al-Assad, Hassan Nasrallah told thousands of his supporters in a televised speech.

Nasrallah, 57, has only made rare public appearances since the 2006 war against his arch-foe Israel. As a figure on Israel's most wanted list, he said in 2014 that he often changed his place of residence in the utmost secrecy.

On Monday, hundreds of Islamic State group fighters and civilians were evacuated from the border region between Lebanon and Syria under a ceasefire deal and headed toward eastern Syria near the Iraqi border.

The truce deal was negotiated between IS and Hezbollah, which has intervened in Syria's six-year war to prop up Assad's government.

The agreement has been criticised inside Lebanon, as well by the US-led coalition fighting IS in Syria and Iraq and especially by Baghdad, which protested that the jihadists were being brought to its doorstep.

Nasrallah tried to justify the deal by saying it was necessary to acquire information about the fate of Lebanese soldiers taken hostage by IS three years ago.

"We have a humanitarian cause. We wish you to help us," Nasrallah said he told Assad. "We can only know what happened to the soldiers through this compromise."

He said that, before approving the deal, Assad responded: "This will make things difficult for me."

The deal came after Hezbollah fought a week-long offensive against IS on Syria's side of the Lebanese border, at the same time as an assault by Lebanese troops on their side of the frontier. 

A US-led coalition spokesman said Wednesday it had carried out air strikes to block the jihadists and their families evacuated two days earlier from reaching their destination in eastern Syria near the Iraqi border.

On Thursday, a source on the ground told AFP that the convoy was back on the road but had changed its route.

It was passing through a regime-controlled area of Homs province and headed for the IS-held town of Mayadeen in Deir Ezzor province instead of the original destination of Albukamal, or a little further from the Iraqi border, the source said.