The Houthis still control the capital and are resisting a push by pro-government forces along several frontlines around the country.
Yemen has been torn by a ferocious war pitting the Houthis and forces fighting for former President Ali Abdullah Saleh against Hadi loyalists, as well as southern separatists, local militias and Sunni extremists.
The conflict escalated in March as a Saudi-led coalition launched airstrikes against the Houthis.
