Boko Haram has claimed responsibility for an attack on a key military barracks in the northeastern city of Maiduguri, in a new video obtained on Monday by AFP that warns of further bloodshed, including against civilians.
"We carried out the attacks in Maiduguri (on March 14)," said a man dressed in white, wearing black headgear and carrying an assault rifle, claiming to be the group's leader, Abubakar Shekau.
The man appeared younger, thinner and with different mannerisms from older videos, which could prompt fresh questions about whether the militant leader, who had previously been reported killed, is still alive.
Shekau has been declared a global terrorist by the United States, which put a $7 million (5.1-million-euro) bounty on his head. Nigeria has separately offered 50 million naira ($300,000) for information leading to his capture or death.
He was reported to have been killed in a gun battle in the northeast between July 25 and August 3 last year, although a man resembling him has featured in a number of videos since then.
Nigeria's military has yet to confirm officially whether Shekau is still alive and defence spokesman Chris Olukolade has said that whoever was making the claims in the videos was immaterial.
"That's not the issue in this matter. They're all terrorists," he told AFP in a March 14 interview.
In the latest video, which was obtained via the same channels as previous statements, the man claiming to be Shekau speaks for 37 minutes in the local Hausa and Kanuri languages, as well as Arabic.
Footage then follows showing what appear to be heavily armed Boko Haram fighters arriving in pick-up trucks and firing on the Giwa barracks with assault rifles and rocket propelled grenades.