Nigeria's President Muhammadu Buhari has replaced his army, navy, air force and defence chiefs, a widely anticipated move as the former general has made crushing Boko Haram his top priority.

"The President has relieved the service chiefs, including the heads of the army, air force and navy of their appointments," Femi Adesina told AFP news agency on Monday.

Major General Abayomi Gabriel Olonishakin, previously head of army training, was named Chief of Defence Staff. The new chief of army staff, T.Y. Buratai, comes from Borno state, one of those worst hit by Boko Haram attacks, and was previously in charge of a multinational joint task force against the insurgents.

Buhari also named a new chief of defence intelligence, Air Vice Marshal Riku Morgan, and a national security adviser, Major General Babagana Monguno.

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The outgoing officials are: Chief of Defence Staff, Air Marshall Alex Badeh; the Chief of Army Staff, Major General Kenneth Minimah; the Chief of Naval Staff, Rear Admiral Usman Jibrin and the Chief of Air Staff, Air Vice Marshall Adesola Amosu, the spokesman said.

Since his inauguration in May, Buhari has moved Nigeria's defence command centre to Maiduguri, the birthplace of Boko Haram, and is setting up the headquarters for a multi-national joint taskforce in Chad's capital N'Djamena.

In June, Amnesty International accused Nigeria's military of systemic human rights abuses and the deaths of 8,000 prisoners and called for an investigation into many top military officials including the army and air force chiefs.

Former President Goodluck Jonathan was heavily criticised for his inability to deal with the six-year Boko Haram violence in the northeast of Africa's biggest oil producer which has killed thousands and displaced 1.5 mn people.

Army morale hit an all time low under Jonathan and it was not until the start of 2015 that the group's fighters were finally pushed out of most areas with the help of foreign mercenaries, troops from neighbouring countries and new equipment.

Boko Haram suicide attacks in Cameroon

At least a dozen civilians and a Chadian soldier were killed in two suicide attacks by suspected Boko Haram fighters in the northern Cameroon town of Fotokol late on Sunday, a senior Cameroonian military officer said.

The first explosion went off inside a bar near a Cameroon special forces (BIR) camp just after sundown, the officer said, asking not to be named.

"The second explosion followed as soldiers approached the bar," he said.

L'Oeil du Sahel, a newspaper in northern Cameroon, said the two attackers wore burqas.

Source: Agencies