UN Secretary-General Antonio Guterres welcomes the swap of about 900 conflict-related detainees in the Yemeni war, said his spokesman on Friday.

"The secretary-general joins the (UN) Special Envoy for Yemen, Hans Grundberg, today welcoming the start of the release operation of conflict-related detainees. Nearly 900 are being released by the parties over three days, starting today," said Stephane Dujarric, the spokesman.

The swap comes under the implementation of the plan agreed by the parties at the last meeting of the Supervisory Committee on the Detainees' Exchange Agreement, which took place in March in Switzerland, he said.

The Supervisory Committee is co-chaired by the office of the UN special envoy and the International Committee of the Red Cross with the parties as members.

The parties have committed to meeting again in May to organize more releases, said the spokesman.

Grundberg said that this release operation comes at a time of hope for Yemen. He urged the parties to immediately and unconditionally release all arbitrarily detained individuals, said Dujarric.

Asked whether the special envoy and the secretary-general believe there are prospects of a broader and permanent deal in Yemen by Eid al-Fitr on April 21, the spokesman said that making calendar predictions is a dangerous game.

"That is not to underestimate the importance of what is happening today and over the next two days, as well as the talks we've seen hosted by the Omani authorities. It is all very hopeful. But it demands a continued political determination from all the parties to rally around and support the UN-supported political process," said the spokesman.

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