A Nigerian militant group tangling with government forces in the country’s southern oil-producing region on Friday declared "an all-out war" after what it said was a deadly bombing raid on civilians. The Movement for the Emancipation of the Niger Delta, in e-mail messages to reporters, said it sank six army gunboats, destroyed three others, and captured three in the restive Niger Delta region. “Many soldiers have been killed and the military has made a hasty retreat,” said the group — which is calling on “men of fighting age to enlist” in its fight against government forces.