GENEVA- Yemen's warring parties have exchanged lists with a total of 16,000 names of people believed to be detained as part of a prisoner swap deal agreed last week, the International Committee of the Red Cross (ICRC) said on Wednesday.

The Iran-aligned Houthi movement and the Saudi-backed Yemeni government are to free prisoners simultaneously next month as part of confidence-building measures agreed at United Nations peace talks in Sweden.*:nL8N1YN5SR

"The parties to the conflict have exchanged lists of 16,000, they now have six weeks to make sure that the lists are accurate, that those people are detained," Fabrizio Carboni, ICRC regional director for the Middle East, told a briefing.

Each side's list had 8,000 names of people they are looking for who may be detained - supposed to reflect "all" people in custody - but some may be dead, missing or duplicates, he said, speaking on return from Yemen.

The operation will require the Saudi-led coalition to guarantee that air space is secure for flights, Carboni added.

Under the agreement, 40 days from the Dec. 11 signing, or Jan. 21, the ICRC will have 10 days to interview privately each detainee released, make medical checks, and arrange transfers to their places of origin by bus or plane, he said.

They are expected to include people in custody outside Yemen and foreigners from "a couple of nationalities" held in the country, Carboni said, declining to elaborate.

(Reporting by Stephanie Nebehay Editing by Mark Heinrich) ((; +41 58 306 2161; Reuters Messaging:; twitter @StephNebehay))