Boko Haram leader Abubakar Shekau speaks at an unknown location in this still taken from an undated video released by the outfit.
Boko Haram leader Abu bakr ShekauYouTube screenshot

After killing at least 20 people in northeast Nigeria on Tuesday, Boko Haram militants released a video that purportedly shows the beheading of a civilian and execution of injured Nigerian soldiers. 

The almost 10-minute long video titled "Attacks by the Soldiers of the Caliphate in West Africa" was released the day the Islamist militant group attacked the northeast Nigerian city of Maiduguri. 

An eyewitness told The Associated Press that the militants laid siege on the city on Tuesday and killed about 20 people.  

It is believed the video may have been shot in the aftermath of the Maiduguri assault. It is also the first video released by the group after taking up the Isis-inspired name - Islamic State's West Africa Province.

In the video, a Boko Haram fighter calls coalition forces from Nigeria, Cameroon, Chad, and Niger as "lying coalition partners who sent their armies against us" and that the Boko Haram is still strong.

"Allah knows the reality on the ground," the fighter says, adding, "Most of our territory is still under control."

The video ends with Boko Haram militants executing injured Nigerian soldiers by shooting them in the head and then beheading a civilian.

It is pertinent here that Boko Haram leader Abubakar Shekau does not make an appearance in the video. The last time he was seen was in a video released in February, in which he had vowed to disrupt the 2015 general elections in Nigeria.

Shekau has featured prominently in most of the group's videos over the last three years and his absence in the latest message has once again sparked rumours of his death.

In the past, the Nigerian army on several occasions had claimed that it has killed Shekau.