Royal Dutch Shell says it has managed to contain the worst oil spill off Nigeria's shores in more than a decade.

The spill on December 20 released 40 000 barrels of oil into the Atlantic Ocean, but Shell said in a statement late on Monday that it had “largely dispersed.”

An investigation was under way and the company said it would continue to monitor the area.

Shell said it did not believe any oil had reached shore. Sapa-dpa