An official of Yemen's Houthi movement said on Saturday the group had received 13 detainees released by Saudi Arabia in exchange for a Saudi detainee freed earlier, ahead of a wider prisoner exchange agreed by the warring sides.

Houthi official Abdul Qader al-Mortada said on Twitter the 13 detainees had arrived in the Yemeni capital, Sanaa, which is held by the Iranian -aligned Houthi group that has been battling a military coalition led by Saudi Arabia since 2015.

The Saudi government media office did not immediately respond to a Reuters request for comment.

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At talks in Switzerland last month attended by the United Nations and the International Committee of the Red Cross, Yemen's Saudi-backed government and the Houthis agreed to free 887 detainees.

"The detainees released today from Saudi prisons are part of the deal agreed via the United Nations, and next Thursday ... the deal will be fully implemented," said al-Mortada, who heads the Houthis' national committee for prisoner affairs.

The U.N. special envoy to Yemen has said the deal is one of several developments reflecting movement towards ending the eight-year conflict that has killed tens of thousands of people and caused a humanitarian crisis.

Saudi and Omani envoys are expected to meet in Sanaa to negotiate a permanent ceasefire deal with Houthi officials, sources have told Reuters, building on an expired U.N.-brokered truce agreement.

Houthi chief negotiator Mohammed Abdulsalam, who is based in Muscat, said on Twitter on Saturday that he had arrived in Sanaa with a Omani delegation.

A visit by Saudi officials would indicate progress in Oman-mediated talks between Riyadh and the Houthis, which run in parallel to U.N. peace efforts, as well as a reduction in tensions after Saudi Arabia and Iran agreed to restore relations.

The Yemen conflict is widely seen as a proxy war between Saudi Arabia and Iran.

The Saudi-led coalition intervened in Yemen months after the Houthis ousted the internationally recognised government from Sanaa in 2014. The Houthis are de facto authorities in North Yemen.