Cameroon's state oil refinery declared force majeure on Saturday, after a storage tank exploded overnight, causing a fire that shut down output at its main refinery in Limbe but caused no deaths.

A letter to its partners seen by Reuters said the fire had "caused a production stoppage at all of our units for a period to be determined."

Cameroon's Sonara refinery, which is almost entirely state owned apart from a 4% stake held by Total, has a capacity of 2.1 million tonnes of crude a year. It serves the whole country, so any delay in getting it back up and running has the potential to cause severe fuel shortages.

It is also a major supplier to the region, including Nigeria, Togo and Ghana, with some products also being exported to the United States and Europe, according to its website.

A Sonara spokesman declined to comment.

On Twitter, the company wrote that "there were no deaths nor injured," in the blast.

A project has been under way for nearly a decade to try to boost its capacity to 3.5 million tonnes, but Sonara has struggled to raise the needed finance.