YOLA, Nigeria, Feb 23 (Reuters) - Nigeria has sealed its northern border with Cameroon in an effort to shut out Islamist militants using its neighbour as a launchpad for attacks, the military said on Sunday.
The closure extends from northern Borno state, by Lake Chad, to the southern end of Adamawa state, around halfway along Nigeria's 1,500-mile border with Cameroon.
Both states are covered by a state of emergency that President Goodluck Jonathan declared last May as part of an offensive meant to crush Islamist sect Boko Haram.
"To effectively curtail the activities of the insurgents, the Cameroon border in the northeast has been closed indefinitely," Brigadier-General Rogers Ibe Nicholas said in a statement.
The Islamists, whose struggle for an Islamic state in northern Nigeria has killed thousands and made them the biggest threat to security in Africa's top oil producer, are currently based in the hilly Gwoza area next to Cameroon.
Nigerian security officials say they often launch deadly attacks then flee over the border to avoid being pursued.
They killed more than 200 people in two attacks last week on villages, prompting renewed criticisms that military action has failed to neutralise them. (Reporting by Imma Ande; Writing by Tim Cocks; Editing by Andrew Roche)