Update: Buhari's meeting with peers on Boko Haram

New Nigerian President Muhammadu Buhari met his regional counterparts in Abuja on Thursday to set up a joint military force against Boko Haram, the latest sign of his intent to crush the Islamist militant group early in his tenure.

The 72-year-old former military ruler, who was inaugurated just two weeks ago, welcomed the leaders of neighbouring Chad, Niger and Benin for the impromptu one-day summit at Abuja airport. Cameroon sent its defence minister.

Entering the meeting, Buhari told reporters Abuja had pledged $100 million to setting up the force, which will be based in the Chad capital Ndjamena but headed by a Nigerian.

However, in a sign of potential diplomatic tensions, he criticised joint proposals discussed among the different countries that would have force commanders rotating every six months.

A rotation would hamper "the military capacity to sustain the push against the insurgents, who also have the uncanny ability to adapt and rejig their operational strategies," he said.

Boko Haram has killed thousands and displaced 1.5 million people during a six-year insurgency aimed at establishing an Islamic state in Nigeria's impoverished northeast.

Until the launch this year of offensives by Chad, Niger, Cameroon and Nigeria, the group, which has pledged allegiance to Islamic State in Syria and Iraq, occupied an area the size of Belgium.

Squashing the insurgency was one of Buhari's main campaign promises, in contrast to his predecessor Goodluck Jonathan, who was accused of dithering and incompetence, particularly after the kidnapping of more than 200 girls from a school in the town of Chibok in April last year.