By Mohammed Ghobari and Angus McDowall
CAIRO/RIYADH (Reuters) - A Saudi-led coalition fighting in Yemen said on Wednesday it had exchanged prisoners with its Houthi opponents and also welcomed a pause in combat on the border, prompting hopes of a push to end the year-long war that has killed some 6,000 people.
Riyadh's confirmation of a rare confidence-building measure in the conflict came a day after senior Yemeni officials said a delegation from the Houthis, who are allies of the kingdom's arch foe Iran, was in Saudi Arabia for talks to end the war.
However, both the Saudi Arabian and Yemeni foreign ministers later said any formal negotiations to end the fighting could only take place under the auspices of the United Nations and must include Yemen's internationally recognized government.
Riyadh and a coalition of Arab states entered Yemen's civil war a year ago in an attempt to restore President Abd-Rabbu Mansour Hadi after the Houthis and forces loyal to former president Ali Abdullah Saleh ousted him from power.
The Saudi state news agency SPA said Yemeni tribal mediators had facilitated the exchange of a Saudi lieutenant captured by the Houthis for seven Yemeni prisoners held in the kingdom.
The agency gave no further details, but some Yemeni media have reported that the exchange happened on the border between the two countries earlier this week.
Quoting a Saudi statement, SPA also said: "The leadership of the coalition forces welcomed the continuation of a state of calm along the border ... which contributes to arriving at a political solution."
After meeting his Gulf Arab and Yemeni counterparts, Saudi Foreign Minister Adel al-Jubeir said he backed U.N. special envoy Ismail Ould Cheikh Ahmed's efforts to resolve the crisis based on U.N. resolution 2216, which calls on the Houthis to return power to Hadi's government.
However, he added in a news conference that the lull was important to deliver aid and medical supplies to people in northern regions of Yemen.
Saleh's General People's Congress party said in a statement it supported any efforts to bring peace to Yemen.
HOUTHIS SNUB IRAN
Yemen's conflict has fallen into a stalemate, in which the Houthis still control the capital Sanaa and other major cities in central Yemen, while its guerrilla forces have shelled and harassed Saudi forces along the rugged northern frontier.
In what could be a goodwill message to Saudi Arabia, a senior Houthi official sought to distance his group from Riyadh's main regional foe Tehran, telling Iranian officials in a Facebook posting to stay out of Yemen's conflict.
"Officials in the Islamic Republic of Iran must be silent and leave aside the exploitation of the Yemen file," said Yousef al-Feshi, a member of the Revolutionary Committee which runs areas of Yemen held by the Houthis.
Asked about the posting, Jubeir said he had not seen it but that it appeared to be a "positive" statement.
Sunni power Saudi Arabia has long accused Shi'ite Iran of trying to expand its influence in Yemen by helping the Houthis, who hail from the Zaydi branch of Shi'ite Islam.
The comments by Feshi, who is seen as close to the Houthis' overall leader Abdel-Malek al-Houthi, were the first snub by the group to Iran, long seen as its main supporter.
On Tuesday, Brigadier General Masoud Jazayeri, deputy chief of staff of Iran's armed forces, suggested that Tehran could send military advisers to help the Houthis in Yemen just as it has done in Syria in support of President Bashar al-Assad's forces.
The coalition spokesman, Brigadier General Ahmed al-Asseri, said Yemeni tribal chiefs had asked for a period of calm to let humanitarian supplies pass through but he declined to be drawn into commenting on the reported visit by a Houthi delegation.
"It is too early to focus on those who are carrying out this role," Asseri told the Saudi-owned al-Arabiya TV. "Let's focus on the result, that there be benefit to our brothers who are affected by what the Houthi militias are carrying out. We do not want to talk about individuals."
Yemeni Foreign Minister Abdelmalek al-Mekhlafi said the talks in Saudi Arabia were "on the intelligence level about prisoners and other issues", adding that peace talks could only happen in accordance with the U.N. resolution.
"This is the only way forward with political negotiations. Anything else is operational and not political," Mekhlafi said after the meeting with his Gulf Arab counterparts in Riyadh.
(Additional reporting by Yara Bayoumy and Noah Browning in Dubai, Omar Fahmy in Cairo, Writing by Sami Aboudi; Editing by Gareth Jones)