ExxonMobil says it has discovered up to 1 billion barrels of oil off Nigeria's shores.

A statement Thursday says the "significant discovery" at Owowo-3 well extends an existing field worked by the U.S. multinational. ExxonMobil is the operator and owns 27 percent of Owowo. Nigeria's state oil company holds majority shares. Other partners include Chevron, France's Total and Chinese-Canadian Nexen.

The news comes the day before ExxonMobil announces third-quarter results.

Oil multinationals in Nigeria are suffering attacks by militants who have slashed production, driving this West African oil giant into recession.

Lagos-based SBM Intelligence risk analysts estimate that ExxonMobil, Dutch-British Shell and Chevron lost $7.1 billion in the first half of this year — some 70 percent of earnings — through militant attacks, low oil prices and weak refinery margins.