Nigeria's security forces failed to respond to several warnings that suspected Boko Haram extremists were on their way to a town where 110 schoolgirls were seized in a mass abduction last month, Amnesty International has said.
The rights group cited security sources, parents and others as saying the military and police received at least five calls in the hours before the attack, which reminded many of the abduction of 276 Nigerian schoolgirls in Chibok by Boko Haram extremists in 2014.
Nigeria's government said it has launched an investigation into the February 19 attack in the northern town of Dapchi, which President Muhammadu Buhari has called a "national disaster".
The military withdrew from the town in January, saying the situation appeared to be calm there.
Witnesses have told the Associated Press that armed fighters arrived in trucks in Dapchi, shouting: "Show us where the school is! Show us where the girls' school is!"
One witness said he knew the men were not soldiers even though they wore military uniforms because their vehicles had Arabic inscriptions.
Parents and educators in Africa's most populous country have raised an outcry in response to the attack, demanding better security for schools in the vast region where Boko Haram's Islamic extremists have kidnapped thousands of people over nearly a decade.
Amnesty International said it interviewed 23 people, including local and security officials, witnesses and girls who escaped.
They said about 50 suspected Boko Haram fighters arrived in a convoy of nine vehicles as villagers were attending evening prayers.
The first warning of the attack came hours earlier, when a phone call was made to the Nigerian army command about 50 kilometres (31 miles) away to say that suspected fighters had been spotted heading to a village near Dapchi, the rights group said.
The military commander responded by saying he was aware and monitoring it, the sources told Amnesty International.
When the fighters later arrived in another village some residents called people in Dapchi to warn that the convoy was headed their way, and one villager said he told the police.
Villagers said the military did not arrive in Dapchi until shortly after the attack, Amnesty International said.
Nigeria's military did not immediately respond to a request for comment.
"If the military disagrees, let them come and say so," the parent of a 16-year-old schoolgirl abducted in the attack, Bashir Manzo, told the AP. He was among those interviewed by Amnesty International.
"If the military knew they were not going to act, they should have informed us and we would have closed the school and asked all the girls to go home," Mr Manzo said, adding that parents have presented their information to the committee set up by Nigeria's president to investigate.
"There were security lapses which the military does not want to admit, but we shall speak the truth about what happened that day."
Amnesty International urged Nigeria's government to make public the results of its investigation into the mass abduction.
"Regrettably, no lessons appear to have been learned from the terrible events at Chibok four years ago," said Osai Ojigho, Amnesty International's Nigeria director.
"What happened in Dapchi is almost a carbon copy of what happened in Chibok, with the security forces failing to respond to warnings - and the same result for another hundred girls and their families."