Boko Haram released a new video Friday denying any suggestion it might surrender, just over a week after shadowy leader Abubakar Shekau appeared in a rare message looking dejected and frail.

Shekau, unseen on camera for more than a year, released an unverified video late last month saying his time in charge of the Nigerian jihadist group may be coming to an end. 

If the video indeed depicts Shekau, he appears thin and listless, delivering his message without his trademark fiery rhetoric.  

It prompted speculation from the army that the Islamist group was on the verge of collapse in the face of a sustained military counter-insurgency.

However, in Friday's message, Boko Haram maintained it was a potent fighting force, with men holding AK-47s posing in front of Toyota Hilux pick-up trucks and a lorry mounted with a military cannon. 

"You should know that there is no truce, there is no negotiations, there is no surrender," an unidentified masked man in camouflage said in a prepared script in Hausa, the dominant language in the north, in the video posted on ouTube.  

"This war between us will not stop."

The video, of markedly better quality than Shekau's and including Arabic subtitles, featured nine masked Boko Haram fighters standing on sandy ground in an undisclosed desert location.

It is unclear if the masked people in the video include the Boko Haram leader. 

Shekau was still the head of the "West African wing", said the masked speaker, likening Boko Haram to the Islamist insurgencies in Iraq, Libya and Syria. 

In March 2015, Boko Haram pledged allegiance to the Islamic State group, another deadly terror organisation.

But there were few signs that Boko Haram -- now styled as Islamic State in West Africa Province (ISWAP) -- has drawn benefits from the partnership. 

Since then Nigeria's army has won back swathes of territory from the militants, liberating thousands of people who had been living under Boko Haram control.

The video appears to confirm collaboration between Boko Haram and the Islamic State group, Africa security specialist Ryan Cummings told AFP. 

"The production quality bears the hallmarks of the Islamic State's media wing," Cummings said, explaining that it is expected that Shekau shun the limelight. 

"A hallmark of the group and its affiliates is that you very seldom see leaders," Cummings said. 

The analyst said it still remains to be seen what support, if any, the Islamic State group is offering to Boko Haram militants on the ground. 

"What we do know is that there has been a pledge of allegiance and we are seeing Boko Haram communiques being spread around cyberspace by Islamic State accounts," Cummings said.

"Whether that has been translated into any operational links in the field, I don't think there's enough verifiable evidence to suggest that."

An estimated 20,000 people have been killed since Boko Haram began its campaign of violence in 2009 to carve out a hardline Islamic state in northeast Nigeria.

More than 2.6 million people have fled their homes since, but some of the internally displaced have begun returning.