Boko Haram leader, Abubakar Shekau, in a new video released on Monday, vowed that the group would defeat a regional force fighting the extremists in North-East Nigeria, Niger and Cameroon.

“Your alliance will not achieve anything. Amass all your weapons and face us. We welcome you,” he said in a 28-minute speech, one of three videos posted by the Islamists on YouTube.

Troops from Nigeria have been backed by soldiers from Chad, Cameroon and Niger in recent weeks, because of increased concerns about Boko Haram’s threat to regional security.

In the second of the latest videos, images of the leader of the Islamic State group, Abu Bakr al-Baghdadi, are shown along with archive footage and a voiceover recalling a battle between British colonial soldiers and fighters from the Sokoto caliphate in northern Nigeria.

Shekau has namechecked al-Baghdadi before, but appeared to be positioning Boko Haram in a wider jihadi context by showing the Sokoto caliphate, which was dismantled by the British in the early 20th century.

“We never rose up to fight Africa. We rose up to fight the world,” he said.

“We are going to fight the world on the principle that whoever doesn’t obey Allah and the Prophet to either obey or die or become a slave,” he added.

The six-year uprising has become a regional crisis and, on Saturday, Nigeria, Chad, Niger, Cameroon and the Republic of Benin agreed to muster 8,700 troops, police and civilians to fight the group.

But Shekau dismissed the size of the force, which had previously been set at about 7,500.

“You send 7,000 troops? Why don’t you send 70 million? This is small. Only 7,000? By Allah, it is small. We can seize them one-by-one. We can seize them one-by-one,” he said in Arabic.

Shekau also directly threatened Chad’s President Idriss Deby, whose forces had attacked Boko Haram in the North-East Nigerian towns of Gamboru and Malam Fatori in recent days.

Shekau’s challenge came after the United States said on Friday that Boko Haram could face a stronger test against more capable regional forces.

Washington estimated that Boko Haram had a core of between 4,000 and 6,000 fighters but is well-equipped after raiding Nigerian Army positions.

A report from Niamey, Niger, on Monday, said that the Boko Haram sect attacked a prison in the country overnight.

The report said the attack happened, hours before Niger’s parliament was due to vote on joining a regional offensive against the militants.

Niger’s parliament was due to vote on Monday on whether to authorise the army to cross the border into Nigeria to participate in the regional offensive.

•Excerpted from a Nigerian Tribune report. Photo shows Shekau.