The fire broke out at 1:10 a.m. (2310 GMT Sunday) in the crude oil section of the western Norway Mongstad Refinery, which is operated by state-controlled Statoil.
Two of the approximately 50 workers at the refinery suffered minor burns and were treated at a nearby hospital.
The cause of the fire, which Statoil called serious, wasn't clear. But workers managed to bring the blaze under control after two hours by shutting off oil flows to the section of the refinery where the fire broke out and letting the remaining crude burn itself out.
Statoil said after the blaze that the refinery was only operating at half its normal capacity, and it wasn't clear when the facility would resume full capacity.
Production at a crude oil terminal that processes petroleum from Norway's offshore oil fields for export wasn't affected.
Norway is the world's third largest oil exporter, and the Monstad refinery, originally built in the early 1970s, was upgraded in the 1980s and 1990s. It is considered a medium-sized facility by European standards.
The nearby raw oil terminal can store as much as 9.4 million barrels of crude, and accommodate large tanker ships.
The refinery is near Bergen, on Norway's west coast, and is about 300 kilometers (185 miles) west of the capital, Oslo.
