Amnesty International has accused the Nigerian army of failing to act on "advance warnings" given a few hours before Boko Haram militants abducted 110 girls from a school in northeast Nigeria last month.
In a new report, the human rights group alleges the army and police received at least five calls on the afternoon of February 19, warning them that gunmen were heading to the Government Girls Science and Technical College in Dapchi town.
"We were not informed... it is not true" Nigerian army says
Boko Haram militants kidnapped 110 schoolgirls last month from Dapchi
It cited evidence from eye witnesses and residents who claimed they alerted Geidam army base in the Nigerian state of Yobe and local police after they saw a convoy of gunmen heading towards the girls' school.
Amnesty has called for an investigation into circumstances that led to the schoolgirl's kidnapping.
"The Nigerian authorities must investigate the inexcusable security lapses that allowed this abduction to take place without any tangible attempt to prevent it," said Osai Ojigho, Amnesty International's Nigeria Director.
Amnesty also criticized the Nigerian army for withdrawing military troops from Dapchi town some weeks before the school was raided.
It said the military's decision meant "the closest personnel were based one hour's drive" from the town. "Why were insufficient troops available? Why was it decided to withdraw troops?," Ojigho asked.
"What measures has the government taken to protect schools in northeast Nigeria? And what procedures are supposed to be followed in response to an attempted abduction?" she added.
Nigeria's military denied their withdrawal led to the raid on the school after it was criticized for redeploying troops from the area.
In a statement, they said their soldiers withdrew because they thought the area was "relatively calm and peaceful."
It handed over Dapchi's security to the Nigeria Police division in the town, the army spokesman said.
Responding to the report Monday, Nigerian army spokesman John Agim told CNN Amnesty's allegations were not true.
"Which of the military base did the residents inform of the impending attack? We were not informed... It is not true," Agim said.
"Because at this time, the military had been redeployed from Dapchi to Kanama January 10 and this incident happened February 19, so how could the residents have phoned to inform the military that had not been in the area for many weeks?" he asked.
Agim accused the human rights organization of publishing reports that frustrate the fight against Boko Haram.
"Amnesty published a report in 2014 that Nigerian army were violating human rights, the United States government refused to supply us weapons to fight Boko Haram because of it," Agim told CNN Monday.
"Now the US government has agreed to supply us weapons, they have brought out another one (report). They should be asked why they are publishing these timely reports," he added.
The Amnesty report also alleges a police source told their team that police fled the town because they feared that Boko Haram fighters would overpower them.
"Evidence available to Amnesty International suggests that there are insufficient troops deployed in the area, and that an absence of patrols and the failure to respond to warnings and engage with Boko Haram contributed to this tragedy," Amnesty's Ojigho said.
"The government's failure in this incident must be investigated and the findings made public -- and it is absolutely crucial that any investigation focuses on the root causes."
Kachalla Bukar whose 14-year-old daughter, Aisha, was taken in the February 19 raid told CNN local police officers deserted Dapchi town when residents reported the incident.
"Even if the military troops were withdrawn weeks before the attack as they (army) says, there are over 30 police officers in Dapchi, there was no action from them that day," Bukar told CNN.
Yobe State Commissioner Abdulmalik Sunmonu told CNN Monday he could not comment on the Dapchi incident anymore.
The military also ignored warnings given some hours before nearly 300 schoolgirls were abducted by Boko Haram from a boarding school in Chibok, Borno State in 2014, the Amnesty report said.
Nigeria's government last year freed five top Boko Haram commanders in exchange for the release of 82 of the Chibok schoolgirls.
However, more than 100 of these girls remain in captivity, and their whereabouts are unknown.
Campaigners from Bring Back Our Girls movement say Boko Haram used similar tactics in the 2014 Chibok kidnappings for the Dapchi school raid.
They questioned why the Nigerian government has yet to prioritize security of schools in northeastern Nigeria, where the terror group has wreaked havoc in the last eight years.
"This is exactly what happened with the Chibok girls abduction. Does the government want to keep playing this game with these savages? Something must be done. We can't keep doing the same thing and expect a different result," Bukky Shonibare, a leading member of the Bring Back Our Girls campaign group, told CNN
"The circle is clear -- they abduct, we negotiate, they collect money and have their men released, and thereafter become more brazened and fortified for more attacks," she added.
Buhari, on a visit to Dapchi last Monday, said the government was investigating circumstances that led to the girls' abduction and warned that "any agency, person or group found to have been negligent or culpable" would be punished.