AT least four police officers were killed in Nigeria's northeast Borno state after a gun battle with suspected Islamist insurgents, a police spokesperson said. Borno has been the heartland of an insurgency by Boko Haram and splinter outfit Islamist State West Africa Province (ISWAP) for more than a decade in the northeast, where they continue to carry out deadly attacks against civilian and security targets. Borno state police spokesperson Nahum Daso Kenneth said the militants had on Friday night attacked Gajiram town in the Nganzai local government area, some 82 kilometres (51 miles) from Maiduguri, the state capital. "Our men…