Dozens of Nigerian students have been killed in their sleep by suspected Boko Haram Islamists in a boarding school.
Police commissioner Sanusi Rufai said the federal government college of Buni Yadi was razed to the ground. Officials revised the death toll upwards from 29 to 59.
The attack took place in Yobe state, near the state capital of Damaturu in the northeast of the country.
"Some of the students' bodies were burned to ashes," said Rufai. All the victims were boys, he added.
Nigerian president Goodluck Jonathan condemned the attack as a "callous and senseless murder by deranged terrorists and fanatics who have clearly lost all human morality and descended to bestiality".
Adamu Garba, a worker at the Sani Abacha Specialist Hospital in Damaturu, detailed the horrific slaughter of male students.
"Students were trying to climb out of the windows and they were slaughtered like sheep by the terrorists who slit their throats. Others who ran were gunned down," he said.
The insurgents want to turn Nigeria into a strict sharia state and their campaign of terror has been waged mainly in the northeast of Nigeria. Three hundred people have been killed in February alone.
The state of Yobe has been placed under emergency rule along with two other predominantly Muslim northeastern states - Borno and Adamawa.
A military campaign to combat the militants has failed.
Boko Haram, which means "Western education is forbidden" is designated a terrorist organisation by the United States and has targeted many schools in the past year.
A similar attack in September killed 40 students when gunmen raided dormitories at night.
Boko Haram's leader, Abubakar Shekau, has claimed in a video that the group would continue its campaign of violence against supporters of democracy and "anti-Islamic" values.