“A short while ago, a fire occurred during the maintenance operations of the Gas Liquefaction Unit No. 32 at the Mina Al Ahmadi refinery,” the company said on Twitter.
The company later announced with “great sadness” that two Asian contractors were found dead at the scene.
“While KNPC expresses its deep sadness and pain for this accident, it extends its deepest condolences to the family of the deceased, wishing a speedy recovery to all the injured.
Seven people were transferred to Al Adan Hospital for treatment, but five with severe burns were later moved to Al Babtain Hospital. Three others were treated at the scene for minor burns.
KNPC said refinery and export functions were not affected by the fire, which occurred at a unit that had been turned off for maintenance.
Ahmadi is Kuwait's biggest refinery, located 40 kilometres south of the capital Kuwait City. It has the capacity to process 466,000 barrels of oil per day.
Kuwait's Minister of Oil, Dr Muhammad Al Fares, visited the site of the fire and spoke to employees, before heading to Al Babtain hospital to check on victims with the Indian ambassador to Kuwait. He said a full investigation into the incident would be launched.
Executive Vice President for Support Services at KNPC, Abdulaziz Al Duaij, praised the "very high professionalism" of the staff who responded to the blaze, saying they were able to deal with the fire in "record time".
Friday's blaze follows a fire at the same refinery in October 2021.