Oil industry officials in Nigeria say militants have kidnapped five more foreign oil workers during a raid that killed two local security guards.
They say gunmen raided an oil company site in Eket late Tuesday in the oil-rich Niger Delta region. The kidnap victims are believed to include nationals of Britain, Romania and Indonesia.
Meanwhile, oil company Royal Dutch Shell said Wednesday that militants have released all 25 of its oil workers who were seized in a raid Monday in Rivers State.
The U.S. consulate in Lagos Wednesday warned Americans to stay away from Rivers State, saying the area has been the site of clashes between militants and Nigerian government forces.
The consulate also cited reports that militants may be planning attacks on Bonny Island, which is used by several foreign energy companies.
In an unconfirmed statement, local militants said they were sending more fighters to the delta region to battle army forces.
Militant attacks have cut Nigeria's oil production by nearly a third this year.
The militants are demanding that Niger Delta communities get a greater share of the region's oil revenue. However, many of the recent kidnappings are believed to have been carried out strictly for ransom.
Some information for this report was provided by AFP, AP and Reuters.