They said the attack targeted a facility used to load tanker trucks with refined products for domestic distribution. The area was on fire and at least five people were killed, the workers said. The number of casualties was expected to rise, they said.
Ras Isa is Yemen's main oil export terminal but no shipments have been leaving since the Saudi-led Arab coalition started an aggression on Yemen in March last year to shore up fugitive former President Abd-Rabbu Mansour Hadi against Houthis.
Local oil workers said the oil exports facilities in the area and a nearby sugar refinery were not affected, Reuters reported.
The United Nations says nearly 6,000 people have been killed in the fighting, but other sources put the number at over 7000, mostly civilians. Hundreds of thousands of people were also displaced by the Saudi-led aggression.