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DUBAI (Reuters) - The Saudi-led coalition in Yemen said that seven Houthi prisoners will be released, after a Saudi prisoner freed by the group arrived in Riyadh on Tuesday, Saudi state television reported.

Saudi prisoner Mousa Awaji was returned on a Red Cross plane from Sanaa on Tuesday due to illness, the Houthi TV channel al-Masirah said, citing Abdulqadir Murtada, a Houthi official.

The United Nations special envoy to Yemen, Martin Griffiths, welcomed the Saudi prisoner release, tweeting that he hoped to see “more similar humanitarian gestures from the parties,” and looked forward to implementation of a prisoner exchange agreement.

Yemen’s warring parties have yet to agree full terms of a prisoner swap, one of the least contentious confidence-building measures agreed at U.N.-sponsored peace talks held in December amid Western pressure to end the conflict.

The United Nations is pushing for the exchange, and the implementation of a ceasefire in the main port city of Hodeidah, to pave the way for a second round of discussions to end a war in which tens of thousands of people have been killed in almost four years.