Nigeria's military is "ransacking" territory it said it has recaptured from Boko Haram in recent months in a search for its elusive leader, the country's defense minister said on Tuesday.

The Nigerian military has said on multiple occasions that it killed Abubakar Shekau, leader of one of two branches of the jihadi group, only for the announcement to be swiftly followed by video denials from someone saying he is Shekau.

"He is on the run so he may be hiding in one of the enclaves of Sambisa Forest," Mansur Dan Ali, minister of defense, told reporters in Abuja.