Nigeria has denied claims it received a warning about an impending attack on a school from which more than 200 girls were abducted.
The accusation has been made by the human rights group Amnesty International which cites interviews with multiple sources.
“We have received credible information from numerous sources in Nigeria that the military were given advance warning that Boko Haram were about to attack the school in Chibok, and that the abduction of the more than 200 schoolgirls could have been prevented,” said Susanna Flood, spokeswoman for Amnesty International.
“They had warning that this school was under threat, and nothing was done to save these girls.”
US actress Angelina Jolie has joined many celebrities in a growing social media campaign for the girls release.
“These men felt they could get away with this, and they can abuse women in such a way, sell them, rape them, take them as property, and because so many people have gotten away with this in the past, because of this culture of impunity,” said Jolie.
“So one of the things we’re working so hard to do is not just do everything we can to bring these girls home, but make sure this stops happening.”
Boko Haram militants, who kidnapped the girls last month, have threatened to sell them.
Experts from Britain, France and the United States have now arrived in the West African state to help the government in the search for those abducted.