MAIDUGURI, Nigeria - Nigerian Islamist militants have overrun an army base in the remote northeastern town of Baga, security sources said on Sunday. Baga is notionally the headquarters of a multinational force comprising troops from Niger, Nigeria, Chad and Cameroon, although only Nigerian troops are actually stationed there. Troops eventually fled the remote station on the semi-desert shores of Lake Chad after it was attacked on Saturday, both sources said. The military was not immediately available for comment.