President Muhammadu Buhari has fired all Nigeria's military chiefs as a multinational army prepares for a fresh onslaught against the West African nation's Islamic extremists.

It was an expected development since Buhari, a former military dictator who was elected in March, has severely criticized the Nigerian military's failure to defeat the Islamic extremists operating mainly in the northeast.

The sacked officers had been appointed in January 2014 when former President Goodluck Jonathan replaced the top military echelon because of failures against Boko Haram.

Jonathan had been accused of being partisan in naming Christians to all but one of the positions in the armed forces traditionally dominated by Muslims. Nigeria is divided almost equally between Muslims who predominate in the north and Christians in the south.

Buhari's announcement on Monday was more even-handed.

Both the new army chief of staff, Maj. Gen. Tukur Yusuf Buratai, and the national security adviser, Maj. Gen. Babagana Monguno, are from northeastern Borno state which is the birthplace of Boko Haram.

Defense chief Maj. Gen. Abayomi Gabriel Olonisakin and navy chief Rear Admiral Ibok-Ete Ekwe Ibas are from the south. The chief of defense intelligence, Air Vice Marshal Morgan Monday Riku, is from the Middle Belt and the chief of air staff, Air Vice Marshal Sadique Abubakar, is from northeastern Bauchi state.

Boko Haram had seized a large swath of northeast Nigeria and declared an Islamic caliphate. A multinational army earlier this year drove the insurgents out of towns and villages but suicide bombings and village attacks have increased, killing more than 250 people in the past two weeks.

The sackings come two weeks before Buhari is to meet with President Barack Obama at the White House in Washington D.C. to discuss more U.S. help in the battle to curb the Islamic uprising that has driven 1.5 million people from their homes and killed more than 13,000 people in six years.

Amnesty International puts the death toll at more than 20,000 to include the deaths of some 8,000 detainees who allegedly died in military custody.

Buhari has promised to investigate Amnesty's allegations. Hundreds of soldiers are being court-martialed for alleged cowardice and desertion. Atrocities committed by the Nigerian military have hampered U.S. help because of laws that prevent the United States from providing certain arms to the governments of armed forces accused of gross human rights abuses.

Buhari inherited a firestorm of problems including a near-empty treasury blamed on corruption and halved prices for the petroleum that provides about 80 percent of government revenue.

Last week, he announced he was halving his salary, putting lawmakers on the spot as their salaries come up for review. But salaries form only a small part of the remuneration as lucrative allowances make Nigerians among the highest paid legislators in the world at nearly $200,000 a year.