Lagos - 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 abducted last month, rights group Amnesty International said on Tuesday.The group cited "credible sources" saying the army and police received at least five calls in the hours before the attack, which reminded many of the 2014 abduction of 276 Nigerian schoolgirls by Boko Haram extremists.Nigeria's government has said it has launched an investigation into the February 19 attack in Dapchi town in the north, 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 there were Arabic inscriptions on their vehicles.Both parents and educators in Africa's most populous country have raised an outcry in response to the Dapchi attack, demanding better security for schools in the 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 in the Dapchi attack. They said about 50 suspected Boko Haram fighters arrived in a convoy of nine vehicles as villagers were attending evening prayers.The first warning came about seven hours earlier, when a phone call was made to the Nigerian army command about 50km 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, sources told Amnesty International.KEEP UPDATED on the latest news from around the continent by subscribing to our FREE newsletter, Hello Africa.FOLLOW News24 Africa on Twitter and Facebook. When the fighters later arrived in another village some residents called people in Dapchi to say the convoy was headed their way, and one villager said he told the police.Villagers said the military did not arrive in Dapchi until after shortly after the attack, Amnesty International said.Nigeria's military did not immediately respond to a request for comment on Tuesday.The rights group urged that Nigeria's government make public the results of its investigation into the Dapchi 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."