The Shiite militia has taken charge of Sanaa, but has stopped short of formally toppling Yemen's government. President Hadi's whereabouts are unknown.
Yemeni President Ali Abdullah Saleh, whose compound was attacked today, appears unable to shut down the unprecedented challenge to his 32-year rule.
Yemen's Houthi rebels claim a Saudi Arabia air strike on Sunday killed 54 people, including women and children. The US is increasingly concerned restive Yemen is becoming a haven for terrorism.
Four clashes in the past eight days underscore the state's vulnerability. Southern secessionists and northern rebels have weakened the central government.