Anglo-Dutch oil giant Shell says it has declared a "force majeure" on crude oil exports from Nigeria as it struggles to repair a sabotaged pipeline.
Shell's subsidiary in Nigeria said the force majeure was effective from Tuesday "due to ongoing repairs on the 48-inch crude export line at Forcados Terminal in the Western Niger Delta".
"Force majeure" is a legal term releasing a company from contractual obligations when faced with circumstances beyond its control.
Shell said the sub-sea pipeline was shut when a leak was discovered on March 4, leading to suspension of crude oil exports through the terminal, which can produce up to 400,000 barrels of crude per day.
Shell has blamed repeated oil thefts and sabotage of key pipelines as the major cause of spills and pollution in the oil-producing region.
Crude oil theft or "bunkering" is a major problem in Nigeria, with estimates that the country loses some $US6 billion ($A6.56 billion) in revenue every year because of the practice.
Nigeria is Africa's largest oil producer, accounting for more than two million barrels per day.