Saudi Arabia said on Wednesday it exchanged prisoners with its foes in Yemen's Houthi movement and that a calm was holding along their border, in signs of unprecedented progress to end their 11-month war.

The statement on state news agency SPA said Yemeni tribal mediators had facilitated the release of seven Yemenis held by the kingdom in exchange for a detained Saudi lieutenant.

An alliance of mostly Sunni and Arab countries launched air strikes and a ground offensive against the Houthis on March 26 after an armed offensive by the Iran-allied group pushed Yemen's internationally backed government into exile.

The conflict had fallen into a stalemate, in which the Houthis still control the capital Sanaa and other major cities in central Yemen while its hardened guerrilla forces shelled and harassed Saudi forces along Yemen's rugged northern frontier.

Saudi state news said the prisoner initiative was launched by Yemeni tribal figures to reduce the violence in the border area and facilitate delivery of badly needed aid, and that the apparent truce could help end the conflict.

"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," SPA reported.

On Tuesday, two officials from a Houthi-run government body in Yemen told Reuters that senior representatives of the group had arrived in Saudi Arabia for peace talks.

The United Nations says nearly 6,000 people have been killed in Yemen's fighting. Hundreds of thousands have been displaced. - Reuters