A Saudi-led military coalition said it had completed a prisoner swap in Yemen, exchanging nine Saudi prisoners for 109 Yemeni nationals, Saudi state news agency SPA said.

Monday’s statement did not say which group the deal was made with, but Yemen’s rebel Houthi movement said on Sunday it had exchanged prisoners with its foe Riyadh, as a first step towards ending a humanitarian crisis prompted by the conflict.

Saudi Arabia received its nationals on Sunday, SPA said.

It did not explain how the Saudis were detained in Yemen, though it said the Yemenis held had been detained in “areas of operations near the border of Saudi Arabia”.

Coalition troops have been battling Houthis for over two years now in support of Yemen’s internationally recognised government.

More than 6,000 people have been killed in the fighting and millions are displaced in Yemen.

Both sides have agreed to a ceasefire at midnight on April 10 ahead of peace talks starting April 18 in Kuwait.