Nigerian militants have detonated a car bomb outside a state government building in the oil-rich Niger Delta region.

Police said no one was hurt in the blast Saturday, which caused some damage to the building in Rivers State.

Militants from the Movement for the Emancipation of the Niger Delta said a second car bomb failed to detonate and was retrieved by fighters. In an e-mail statement, the group warned of future attacks on local government officials accused of, in its words, "sabotaging" efforts at resource control.

Elsewhere in the Delta region Saturday, Nigerian officials said an explosion damaged a water supply pipeline that feeds an oil refinery.

Nigerian militants carry out frequent attacks and kidnappings at oil sites to press for a greater share of oil revenue.

The violence has sharply cut oil output in Africa's top oil-producing nation.

Some information for this report was provided by AFP, AP and Reuters.