Nigeria and its neighbours agreed on Thursday (11 June) to set up a joint military force to counter Boko Haram, a sign of President Muhammadu Buhari's intent to crush the Islamist militant group during his tenure.

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

Aliyu Ismail, the permanent secretary of Nigeria's minister of defence, said the joint force, based in the Chad capital N'Djamena, will be running by 30 July.

"The heads of state and government of Lake Chad Basin Commission and Benin Republic took the following decisions: approve the concepts of operations, strategic and operational and related documents of the multinational joint task force for the fight against Boko Haram terrorist groups; approve the immediate deployment of the multinational joint task force headquarters at N'Djamena, Chad, by implementing its human, logistics and financial requirements; approve the development of the national contingent with the multinational joint task force under the operational command of the multinational joint task force commander assisted by his joint headquarters by 30 July, 2015," Ismail told a news conference in Abuja.

The joint force will have a permanent Nigerian leader, a concession to Buhari's opposition to rotating commanders.

Changing the force's leadership 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," Buhari said before the meeting.

Chad and Cameroon have deputy commander and chief of staff posts in the force, whose mission is to crush Boko Haram, which has killed thousands and displaced 1.5 million people in its six-year fight to establish an Islamic state in Nigeria's north east.

Buhari also promised to look into the recent claims by Amnesty International that Nigeria's military have committed war crimes during the campaign against Boko Haram.

"Our commanders, mainly Nigerian commanders, have been accused of ill treating Boko Haram. The context of Boko Haram killing tens of thousands of Nigerians was not an issue, but the issue is that Nigerian commanders have allowed their troops to maybe kill some Boko Harams or ill treated them while they were in camps. I believe the military hierarchy is investigating the case, since the allegation is made by the Human Rights Commission," said Buhari.

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.

In his two weeks since assuming office, Buhari has focused on little else, travelling to Niger and Chad and shifting the military command centre from Abuja to Maiduguri, the capital of north-east Borno state and birthplace of the insurgency.