Nigeria's new president, Muhammadu Buhari, on Wednesday promised to look into an Amnesty International report urging the International Criminal Court to probe senior military officers for war crimes in the battle against Boko Haram.

"I assure you that your report will be looked into," an official statement quoted Buhari as saying in Niger's capital Niamey, in his first reaction to the group's 133-page report.

"This administration will leave no stone unturned to promote the rule of law and deal with all cases of human rights abuses," he said in the statement issued by his spokesman, Shehu Garba.

Buhari is on an official visit to neighbouring Niamey, with the deadly Boko Haram insurgency set to feature high on the agenda in talks with Niger officials.

The new Nigerian leader, who took office last week after becoming the first candidate to unseat a sitting president, has made the fight against Boko Haram a priority, vowing to rid his country of "the terror" of the Islamist fighters.

"Respect for human rights and adherence to the rule of law are the life and soul of the democratic system. We will not tolerate or condone impunity and reckless disregard for human rights," the statement added.

Amnesty International on Wednesday said senior military figures should be probed for the extra-judicial murders of hundreds of people and the deaths of thousands of others while in detention, including from torture and starvation.

Amnesty's secretary general Salil Shetty described the abuses as "sickening" but Nigeria's military hit back saying the report was designed to besmirch its reputation.

"In the course of security operations against Boko Haram in northeast Nigeria, Nigerian military forces have extra-judicially executed more than 1,200 people; they have arbitrarily arrested at least 20,000 people, mostly young men and boys," the report said.

Nigerian forces have in recent years "committed countless acts of torture; hundreds, if not thousands, of Nigerians have become victims of enforced disappearance; and at least 7,000 people have died in military detention as a result of starvation, extreme overcrowding and denial of medical assistance", it added.

The London-based watchdog said commanders based in the northeast "should be investigated for potential responsibility for war crimes of murder, enforced disappearances and torture".

Military spokesman Major General Chris Olukolade rejected the Amnesty claims and said "the Nigerian military does not encourage or condone abuse of human rights neither will any proven case be left unpunished."