A man who identified himself as Shekau said in a video sent to news agencies on Thursday that the Islamist group had "not been flushed out of anywhere."

"If you indeed crushed us, how can you see me like this?" he added during the 25-minute video, speaking in the Hausa and Arabic languages.

The Boko Haram leader accused Nigerian President Muhammadu Buhari of "telling lies to the people," after Buhari said on Christmas Eve that the extremist group had been defeated and driven from the forest.

"How many times have you killed us in your bogus death?" he asked, in footage he said was filmed on Christmas Day.

Nigeria's military has said it has killed or wounded Shekau on multiple occasions in recent years, often followed by video denials by someone who claims to be Shekau. But poor quality footage makes it hard to confirm if the person is the same man as in previous videos.

Boko Haram has waged an uprising against the Nigerian state for the past seven years, which has often spilled over to neighboring West African states. More than 20,000 people have been killed and around 2.6 million have been displaced.

The extremist group is also reported to be in the grip of a power struggle between Shekau and Abu Musab al-Barnawi, the 22-year-old son of the group's founder Mohammed Yusuf. Barnawi was said to have replaced Shekau as leader in August.

mm/kms (AFP, Reuters)