The warring sides in Yemen's long conflict have agreed to exchange 1,081 prisoners, the United Nations mediator said on Sunday following talks in Switzerland.

Yemen's government, which is supported by a Saudi-led military coalition, and Iran-backed Huthi rebels resolved to swap some 15,000 detainees as part of a peace deal brokered by the UN in Stockholm back in 2018.

The two sides have since undertaken sporadic prisoner exchanges, but the release of over 1,000 loyalists and insurgents — if it materialises — would mark the first large-scale handover since the war erupted in 2014.

"I am personally extremely pleased to be here to announce that you have reached a very important milestone," UN Envoy Martin Griffiths said at the end of the talks at the Swiss village of Glion, overlooking Lake Geneva.

Griffiths hailed the decision to release the prisoners as the largest such operation during Yemen's conflict.

He also congratulated the government and the Houthis for renewing their "commitment to the full implementation of the Stockholm agreement".

The Houthi-run Al Masirah TV channel quoted a rebel source as confirming a deal had been reached and that both parties "express their commitment to implement the agreement".

"What matters to us is implementing the deal, not only signing it," senior rebel commander Mohamed Ali Al Houthi had tweeted on Saturday.

Yemen's Foreign Minister Mohammad al-Hadhrami welcomed the deal as a "humanitarian" breakthrough, but also said in a tweet that "the government demands the agreement is implemented without stalling".

'Reason to be wary' 

Dr Elisabeth Kendall, a researcher at the University of Oxford's Pembroke College, said the deal was an "important trust-building measure" amid efforts to end the Yemen conflict, but one that would create more animosity if it faltered.

"This step has to be viewed positively, given how polarised the warring sides now are and how intractable the conflict has become,” she told AFP.

"But there are several reasons to be wary... We have been here several times before. Prisoner swaps are agreed, then they come to nothing and those impacted end up even more frustrated and angry.”

Sources on both sides had told AFP Saturday that a deal had been reached for the prisoner exchange, indicating it was to be implemented within two weeks.

The agreement includes the release of "681 rebels and 400 government forces [and allies], among them 15 Saudis and four Sudanese”, a member of the government delegation told AFP.

The talks began on September 18, and had been aimed at securing the release of 1,420 prisoners, including the brother of Yemeni President Abed Rabbo Mansour Hadi.

Griffiths did not provide details on which prisoners would be exchanged under the agreement reached in Glion.

But the government official told AFP that the release of General Nasser Mansour Hadi from the hands of the rebels "has been postponed”.

The International Committee of the Red Cross is to oversee the return of detainees to their families.

Fabrizio Carboni, head of the ICRC’s Middle East and Near East operations, described the agreement as "a very positive step”.

"This release will alleviate the suffering of many detainees and many families who have been waiting for so long to be reunited,” he said at the Glion ceremony.

"We are convinced that this release... will contribute to renew solid, valid peace talks.”

Tens of thousands of people, mostly civilians, have died in the Yemen conflict, which has sparked what the United Nations calls the world’s worst humanitarian crisis.