Human Rights Watch says Nigeria's new government is violating rights on many fronts in its fight against Boko Haram's Islamic uprising and in bringing corrupt politicians to book.

The allegations in the New York-based organization's global report published Wednesday offers fuel to opponents who accuse President Muhammadu Buhari of acting as he did as a former military dictator.

The report says Buhari's inauguration in May "has not diminished the potency of the country's serious human rights challenges."

Buhari has not acted on promises to investigate allegations that the military is committing extrajudicial killings and illegally detaining people suspected of being Boko Haram fighters or supporters.

Human Rights Watch said the worst atrocity of 2015 in Nigeria was Boko Haram's slaughter of 2,000 civilians in Baga, a northeastern fishing settlement.