Seven Lebanese soldiers being held by militants in the Arsal region on the Syrian border were freed on Thursday after a truce deal, the official National News Agency said.

The NNA said the seven were freed in an army operation, although there was no immediate confirmation from the military.

The releases came after a delegation of Sunni clerics said it had negotiated a deal under which militants who have been fighting the army in the area since Saturday would withdraw and turn over prisoners.

On Wednesday night, chief negotiator Sheikh Hossam al-Ghali said the militants, believed to be from several jihadist groups operating in Syria, had begun retreating.

"Fighters in Arsal have started to head across the Lebanese border" into Syria, Ghali said.

He said a ceasefire would be in place until 7:00 pm on Thursday (1600 GMT), following an agreement between Lebanon's prime minister, the army and other parties.

Another negotiator and fellow cleric, Samih Ezzedine, said the militants had agreed "to leave Arsal completely within 24 hours".

"They asked not to be shot at as they withdraw, and if that happens the whole agreement will be in jeopardy," he said.

"All the prisoners are alive and despite difficult negotiations we have clear and positive promises they will be released. I hope that will happen on Thursday," Ezzedine said.

At least 22 soldiers and 20 policemen were reportedly taken hostage by the militants, who attacked troops in the Arsal region of eastern Lebanon on Saturday.

Another 17 soldiers have been killed, and more than 80 wounded in the fighting, which is the worst violence in the area since the conflict in neighbouring Syria began in March 2011.

The UN agency for refugees, the UNHCR, has said it received reports from field hospitals in Arsal of at least 38 people killed and more than 250 wounded in the fighting, but there was no official confirmation of this.

The tension has spread to the northern Lebanese city of Tripoli, where an explosive device detonated on Wednesday night, killing one person and wounding six, a security source said.