The explosion was caused by two air strikes by the Saudi-led coalition, the Houthi Ansarullah movement said, according to Saba news agency.
Hudaydah, which lies some 145 kilometers (90 miles) southwest of the capital Sana’a, is a lifeline gateway for food, fuel and humanitarian aid.
The United Nations last month warned that thousands of Yemeni civilians were at risk in the western Hudaydah province after fighting escalated.
Last month Yemen army and Houthi Ansarullah fighters fought with forces loyal to fugitive former president Abd Rubbuh Masur Hadi south of the port in some of heaviest clashes since a UN-negotiated truce in 2018.
It comes amid heavy fighting in the Ma’rib region, some 120 kilometers (75 miles) east of Sana’a, as Houthi forces seek to wrest control of the pro-Hadi forces’ last northern stronghold.
The war on Yemen launched by the Saudi-led coalition has claimed tens of thousands of lives and displaced millions, according to international organizations, sparking what the UN calls the world's worst humanitarian crisis.