BEIRUT: Al Qaeda's Syrian affiliate, Al-Nusra, on Tuesday freed 16 Lebanese soldiers and police it had held for more than a year in exchange for the release of prisoners and delivery of aid.

The exchange brought a partial end to a hostage crisis that has haunted Lebanon since jihadist groups overran the eastern town of Arsal on the Syrian border in August 2014.

Another nine soldiers and policemen remain in the hands of the militant Islamic State (IS) group, with uncertainty over whether negotiations to free them can succeed.

The 16 hostages — 13 policemen and three soldiers — were transferred from territory held by Al Qaeda affiliate Al-Nusra Front on the mountainous border with Syria by Lebanon's Red Cross.

Television footage showed the men, sporting long beards and hair in some cases, boarding four Red Cross vehicles before being driven to an army checkpoint.

Around them, armed and masked Al-Nusra fighters waved the group's black flag and chanted slogans.

In a statement, Lebanon's General Security service confirmed the 16 had been released and pledged "no efforts will be spared to secure the return of those held by Daesh," using the Arabic acronym for IS.

In exchange for the hostages, Lebanon freed 13 prisoners, among them Saja al-Dulaimi, the former wife of IS chief Abu Bakr al-Baghdadi, and handed over several trucks of humanitarian aid.

A security source told AFP that 10 of the prisoners had chosen not to be transferred to Al-Nusra and would be returned to Beirut.

Dulaimi appeared to be among that group, telling Al-Jazeera television in an interview during the exchange process that she wanted to go to Beirut and possibly on to Turkey.

Joy, and agony

In downtown Beirut, where relatives of the kidnapped servicemen have manned a protest camp since they were seized, there were tears of joy and relief.

Relatives gathered around televisions to watch as their sons, husbands and brothers prepared for their release.

Several screamed and ululated and even broke into the Middle Eastern dance known as debke to express their joy.

Others distributed sweets, and threw petals and rice into the air.

"I've been awake day and night for the last few days, because there were positive signs," said Marie Khoury, whose brother George was among the released men.

"There will be seven days of drumming and celebrations in Kobayat," she said, of their ancestral village.

But she added: "Our joy is incomplete without the release of those held by the IS group and we hope that the Lebanese state will intensify its efforts for their release."

Amid the celebrations, the mother of one of the IS hostages came to congratulate the families of those being freed, but quickly dissolved into tears.

"Don't forget about us," she pleaded with them, as they assured her they would continue to pressure the Lebanese government to secure the release of the remaining hostages.

The prisoner exchange comes 16 months after Al-Nusra and IS briefly overran the town of Arsal on Lebanon's eastern border with Syria after clashes with Lebanese troops.

The groups withdrew under a truce deal, but took 30 hostages with them.

Four of the hostages were subsequently executed by the two groups, including Mohammed Hammiya, whose body was turned over to Lebanese authorities on Tuesday morning in the first stage of the deal.

A fifth died of wounds sustained in the Arsal clashes shortly after he was taken hostage.

In recent days, there had been a flurry of reports of an imminent deal and the exchange appeared set to take place on Sunday before collapsing at the last moment, reportedly after Al-Nusra added new conditions.