Updated

Witnesses say the Islamic extremists of Boko Haram are seizing more towns along Nigeria's northeastern border with Cameroon and adopting a new strategy of encouraging civilians to stay as they carve out an "Islamic caliphate" under their black and white flag.

Fleeing resident Michael Kirshinga said Nigerian army soldiers ran away when hundreds of insurgents in stolen military armored personnel carriers, trucks and motorcycles attacked Gulak, an administrative headquarters of Adamawa state. He and others said the rebels also seized nearby Duhu, Shuwa Kirshinga and other towns over Friday night and Saturday.

Boko Haram now holds a string of towns in the northeastern states of Adamawa, Yobe and hardest-hit Borno. The new seizures come as the United States announced a major border security program for Nigeria and its neighbors.