Nigerian militants who recently kidnapped nine foreign oil workers have carried out more attacks in the oil-rich Niger Delta region.
The militants said Monday that they used explosives to destroy a houseboat belonging to the Nigerian army and an oil pipeline operated by Shell Oil company.
Shell confirmed the attacks, saying the houseboat was abandoned and that the militants destroyed a pipeline switching station known as a "manifold."
The militant group, known as the Movement for the Emancipation of the Niger Delta seized the oil workers on Saturday, during raids that damaged pipelines and a key oil loading terminal.
The attacks have forced Shell to cut back oil production by 455,000 barrels per day.
The militants are demanding greater local control over the Niger Delta's oil wealth, as well as the release of two jailed ethnic Ijaw leaders.
Nigeria's government says the militant movement is a cover for criminals stealing oil from pipelines across the Delta.
The U.S. State Department has called for the unconditional release of the hostages, who include three Americans, two Egyptians, two Thais, a Briton and a Filipino.Some information for this report was provided by AP and Reuters.