The US-led coalition carried out two sets of air strikes on Wednesday to block Islamic State group fighters evacuated from Lebanon from reaching eastern Syria, its spokesman told AFP.

Hundreds of IS fighters and civilians were evacuated Monday from the border region between Lebanon and Syria under a ceasefire deal and were headed to an IS-held town near Syria's eastern frontier with Iraq.

A first set of strikes hit the road leading from the Syrian town of Hmaymah to the IS-held town of Albukamal further east, said coalition spokesman Colonel Ryan Dillon.

"To prevent the convoy from moving further east, we cratered the road and destroyed a small bridge," he told AFP.

The coalition then carried out a second set of strikes that "struck individual vehicles and fighters that were clearly identified as IS" and appeared to be moving towards the convoy from Albukamal.

"If they continue to try to send people that way, then we'll continue to strike them. It could be a running tally," Dillon said.

"IS is a global threat; relocating terrorists from one place to another for someone else to deal with is not a lasting solution."

The evacuation deal was negotiated between IS and powerful Lebanese Shiite movement Hezbollah, which has intervened in the war in neighbouring Syria to prop up the Damascus government.

Hezbollah fought a week-long offensive against IS on the Syrian side of the Lebanese border, coinciding with a simultaneous assault by Lebanese troops on their side of the frontier.

The battles ended Sunday with the announcement of the deal to bus IS forces hundreds of kilometres (miles) from Syria's western border with Lebanon to its eastern frontier with Iraq.

- Civilians aboard convoy -

Jihadists and civilians, including children, left the border region two days ago, but on Wednesday their buses were still held up at Hmaymah.

The Syrian Observatory for Human Rights said the convoy was looking for a "new route" to reach Albukamal after the coalition strike.

Dillon said the US-led alliance was monitoring the convoy in real time and its last known location was near Hmaymah.

"If we are able to strike them without harming civilians, then we will do so," Dillon said.

Asked whether the presence of civilians had prompted the coalition to bomb the road instead of the convoy itself, Dillon said that would be "consistent" with protocol.

There was no immediate reaction to the strike from Hezbollah or from Syria's government.

The evacuation agreement had sparked a furious reaction from the United States, which considers Hezbollah to be a "terrorist" organisation.

"Irreconcilable #ISIS terrorists should be killed on the battlefield, not bused across #Syria to the Iraqi border without #Iraq's consent," US presidential envoy to the anti-IS coalition Brett McGurk said Wednesday.

"Our @coalition will help ensure that these terrorists can never enter #Iraq or escape from what remains of their dwindling 'caliphate'," he wrote on Twitter.

- Iraq lambasts deal -

It was also met with outrage in Iraq, with Prime Minister Haider al-Abadi describing it as "unacceptable" and an "insult to the Iraqi people".

Hezbollah chief Hassan Nasrallah issued a rare written statement late Wednesday in an attempt to tamp down the controversy.

"We transferred these defeated fighters from a front where we are battling to another front where we are battling," he said.

"Our fight and our fate are one," Nasrallah said, addressing Iraqi officials.

Lebanese opponents to the deal were angry that IS fighters were travelling "on air-conditioned buses" after having been suspected of killing Lebanese troops.

On Wednesday, Lebanon's president and the chief of the army hailed the "victory" against IS.

"Today, we are announcing Lebanon's victory against terrorism. I dedicate this victory to all Lebanese, who can be proud of their army," President Michel Aoun said.

After Sunday's deal, IS fighters who had surrendered led Lebanese authorities to human remains believed to belong to Lebanese soldiers kidnapped by IS in 2014.

Source: AFP