Nigerian terror group Boko Haram appears to be increasingly modelling itself on Islamic State, and there are fears it could be seeking an alliance with the group.

The US wants to prevent those murky ties from solidifying.

Special forces commander for West Africa, Colonel George Thiebes, fears they will all coalesce.

"If they're separate, divide and conquer would be an easy approach to do that.

"That's why again, focus on a regional approach, help isolate it and to prevent that from happening."

CNN's Arwa Damon says the extremist group, which is at war with both Chad and Nigeria, is intent on establishing its own Islamic State in Africa.

"It increasingly appears that Boko Haram is trying to model itself after ISIS - declaring its support but not yet its allegiance."