A fire broke out at the Houthi-controlled Yemeni port of Hodeidah early on Saturday, destroying warehouses filled with cooking fuel and foodstuffs, port workers said.
They told Reuters that, as of 1100 GMT, fire trucks had not been able to put out the blaze in the warehousing area, which they said appeared to have been caused by an electrical short circuit.
Reuters television footage showed thick plumes of smoke rising into the air and fire fighters dousing flames.
Hodeidah port, on the Red Sea, handles the bulk of Yemen's imports, including critically-needed food and aid supplies. The three-year war in the country, which was already the Arab world's poorest, has pushed it to the verge of famine.
"The fire destroyed huge amounts of fuel and humanitarian aid and foodstuff," a UN World Food Program (WFP) employee told Reuters by telephone, adding that there would be an investigation to determine the cause.
The Houthi-run Saba news agency reported the fire at the port, but did not mention the cause.
Workers said the warehouses also contained hundreds of thousands of mattresses meant for those displaced by the war, which has killed more than 10,000 people and crippled the economy. The United Nations says that three out of four Yemenis - 22 million civilians - need relief aid.
A Saudi-led coalition intervened in Yemen's civil war in 2015 to restore the internationally recognized Yemeni government that was forced into exile by the Iran-aligned Houthis.
Late year the coalition, under international pressure, eased a three-week blockade imposed on Yemeni ports and airports in November in response to a ballistic missile fired by the Houthis toward the Saudi capital, Riyadh.