Tom Batchelor, Express, March 13, 2015

In an audio message reported to be from IS, the fighters claimed their aim of creating an Islamic government, or caliphate, had been achieved.

In the 30-minute tape, which has yet to be verified, spokesman Mohammed al-Adnani said: “We announce to you to the good news of the expansion of the caliphate to West Africa because the caliph . . . has accepted the allegiance of our brothers of the Sunni group for preaching and the jihad.”

The confirmation follows a pledge from Boko Haram last week to ally with IS, whose influence until now has been limited to North Africa and the Middle East.

Boko Haram’s leader said in a clip released on Saturday: “We announce our allegiance to the caliph . . . and will hear and obey in times of difficulty and prosperity.”

Experts believe the pledge could boost their propaganda message as both groups seek to attract converts from around the world, using social and conventional media.

Although it is unlikely to boost the groups’ bid for more territory.

“It is by no means certain that these announcements will have any significance on an operational level,” Cathy Haenlein, a research analyst at defence and security think-tank the Royal United Services Institute said.

“On a symbolic level, the formal pledge and its acceptance serve to enhance the visibility and jihadist credential of Boko Haram and bring it a greater share of the global spotlight.

“It allows Islamic State to demonstrate growing strength and expansion in the face of ongoing military operations against it.”

Boko Haram–which means ‘Western education is forbidden’ in English–previously claimed responsibility for kidnapping and enslaving 219 Nigerian school girls in a mass abduction last April.

The girls’ plight sparked worldwide concern with many high-profile figures leading a ‘#BringBackOurGirls’ campaign.

The sub-Saharan Islamist group has in the past welcomed pledges of allegiance from like-minded groups in Egypt, Algeria and Libya.

The group, founded in 2002, initially focused on opposing Western-style education before launching military attacks in Nigeria and neighbouring countries in 2009.

However its militants have up to this point failed to match the success IS has had in seizing large tracts of land.

Estimates put the number of people killed by the group at 13,000, with a further 1.5 million people left homeless.

Dr. Natasha Underhill, an expert on Middle Eastern and International terrorism at Nottingham Trent University, agreed that today’s announcement was part of a strategy to promote the group around the world.

“We have a lot of alliances and allegiances declared by African states and some are saying that with Boko Haram want to pledge allegiance to ISIS now,” she said.

“I think thats only for propaganda use and figurehead use essentially, ISIS don’t want to have these groups associated with them because they are too messy in their structure.”

IS has had even more luck forging links with militant groups across the Arabian peninsula and controls the strategic cities of Tikrit and Mosul in Iraq, despite pressure from Iraqi and Western forces in recent months.

IS spokesman Al-Adnani played down recent victories by coalition forces in the latest audio clip to be released, following an announcement from the Ministry of Defence last week that it had conducted successful raids on militants in the west of Iraq.

RAF jets have carried out attacks on the group in Iraq since September, but Parliament voted against conducting operations in the skies above Syria in a landmark vote.

Last month, a committee of MPs described the UK’s role in the fight against IS as “strikingly modest”, urging the Government to step up its military response.

British military personnel are involved in training Iraqi and Kurdish Peshmerga forces, but have so far avoided engaging in any ground combat operations in the country.