Yemeni Shi'ite rebels freed a Saudi soldier on Monday, handing him to a ceasefire committee in a goodwill gesture, a Yemeni official said.
Talks were underway to free the remaining four Saudi soldiers believed held captive, Al Arabiya television said.
The move came days into a truce between Sanaa and the northern Shi'ite rebels. The insurgents and the Yemeni and Saudi governments have sought in recent weeks to wind down fighting as pressure mounted on Sanaa to focus on a bigger threat: al Qaeda.
He is released, the Yemeni official said of the soldier let go on Monday, adding the insurgents expected rebels held prisoner by Sanaa and Riyadh would also soon be freed. There was no immediate comment from Saudi Arabia.
Saudi Arabia, the world's top oil exporter, was drawn into conflict with Yemeni rebels in November when the insurgents seized some Saudi territory, accusing Riyadh of letting Yemeni troops use Saudi land to launch attacks against them.
Saudi Arabia on Saturday gave the rebels, whose main foe is Yemen's central government, 48 hours to free the prisoners.
Al Arabiya broadcast images of the freed soldier, named as Yehya Abdulla Al Kosaae, lying in a bed and engaged in a conversation. His lower body was covered by a sheet.
Riyadh has said handing over the soldiers would help prove the rebels are serious about ending the fight with Saudi Arabia. The insurgents have been fighting Sanaa on and off since 2004 complaining of social, religious and economic discrimination.
Saudi-owned Asharq al-Awsat newspaper quoted an unidentified Yemeni security official on Sunday as saying the handover of the soldiers, also part of a truce agreement with Sanaa, was expected to be completed in less than a week.
Last month, Yemen's Shi'ite rebels offered Saudi Arabia a truce and said they had left the kingdom's territory. Riyadh later declared victory over the rebels.
U.S. WELCOMES TRUCE
The northern rebels agreed on Thursday to a truce with Sanaa, which had come under pressure to ramp up a crackdown on a resurgent al Qaeda after a failed December attack on a U.S.-bound plane claimed by al Qaeda's Yemen-based wing.
But the Yemeni government, which has escalated airstrikes and targeted leaders of the global militant group, is overstretched from its fight with northern rebels and its bid to contain southern secessionist sentiment.
Riyadh and Western powers fear Yemen may become a failed state and that al Qaeda could exploit the ensuing chaos to use the country as a base for attacks in the region and beyond.
U.S. Secretary of State Hillary Clinton, visiting the Gulf Arab region, welcomed the ceasefire between the rebels and central government and said Washington was concerned about the humanitarian situation in north Yemen, where about 250,000 people have been displaced.
We understand that a mediation commission representing all parties is monitoring compliance with the terms of the ceasefire and beginning the urgent process of reconciliation and reconstruction needed to bring this conflict to a permanent end, Clinton said in a statement.
The United States supports a unified, stable, democratic and prosperous Yemen. We have significantly increased assistance to address the political, economic and security challenges that Yemen faces, and the president requested further increases in his recent budget proposal, she said.
Some violence has continued despite the northern truce. Seven Yemenis, two soldiers and five civilians, were killed when a land mine exploded on a road in a suburb of the rebel stronghold of Saada, a tribal source said on Monday.
Yemen's foreign minister has been quoted as saying Sanaa was operating on the basis that the rebels were serious about wanting to end the war, but that it was normal for any truce to see some violations.
(Writing by Cynthia Johnston; Editing by Janet Lawrence)