Yemen’s warring parties have agreed to a prisoner swap, United Nations special envoy Martin Griffiths said in Sweden on Thursday. The move would allow thousands of families to be reunited, Reuters quoted the diplomat as saying. The Yemeni government on Thursday demanded rival Houthi rebels withdraw from the flashpoint port city of Hodeida. The statement came less than two hours before UN-brokered peace talks were due to open in Sweden. The warring sides are meeting at a castle in the Swedish town of Rimbo, north of Stockholm. Griffiths has said the desperate situation in Yemen includes a prospect of famine.