More than 150 people are reported to have been killed since troops and militiamen stepped up a ground assault on the city's outskirts last Thursday.
The UN and charities say the fighting is also endangering medical facilities and hundreds of thousands of civilians.
Hudaydah's port is a lifeline for millions of Yemenis at risk of famine.
Up to 80% of the humanitarian supplies, fuel and commercial goods on which they depend are delivered through the facility. UN officials have warned that the toll in lives could be catastrophic if it is damaged, destroyed or blocked…