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LAGOS, Nigeria -- The international effort to rescue the 276 schoolgirls being held captive by Islamic extremists in northeastern Nigeria was boosted Friday when British security experts joined the Nigerian and American forces trying to rescue the missing students.
As the worldwide effort got underway the weakness of the Nigerian military was exposed in a report issued by Amnesty International.
Britain said its aim was not only to help with the current crisis but to defeat Boko Haram.
"The team will be considering not just the recent incidents but also longer-term counter-terrorism solutions to prevent such attacks in the future and defeat Boko Haram," the Foreign & Commonwealth Office said in a statement Friday.
The American team was joined by six additional military officers and more are expected soon, said Pentagon spokesman Navy Rear Adm. John Kirby. The U.S. officers will do a "gap analysis," an assessment to identify what the Nigerian military needs that the U.S. could provide in the search for the girls, he said.
Hostage negotiations is another area where the American team will assist, said U.S. State Department spokeswoman Jen Psaki.
China, France and Spain have also promised help.
Demonstrations in support of the missing Nigerian girls have been held around the world and a social media campaign --dubbed #BringBackOurGirls -- continued to grow.
In New York, the U.N. Security Council hinted at sanctions against Boko Haram. In a strongly worded statement, the council condemned a May 5 attack that killed and injured hundreds and demanded the immediate release of the kidnapped girls.
Council members also expressed their intention to consider possible sanctions against Boko Haram.
The weakness of the Nigerian armed forces was highlighted Friday in a report which said the military did not respond to warnings that Boko Haram rebels were about to attack Chibok, the town where the young women were abducted from their school.
Nigerian security forces had four hours of notice about the April 15 attack by the rebels but did not react because of their fear of engaging the extremists, said Amnesty International, in a report citing multiple interviews with credible sources.
"This abduction could have been prevented," Amnesty spokeswoman Susanna Flood said of the Nigerian military's inaction.
The mass kidnapping of the schoolgirls has focused the world's attention on Boko Haram and on the response of President Goodluck Jonathan's government.
"I believe that the kidnap of these girls will be the beginning of the end of terror in Nigeria," said Jonathan at an economic forum on Thursday.
Jonathan's government is accused of being slow to mount operations to rescue the girls, who were kidnapped on April 15, charges the government vehemently denies. The military said in a strong statement late Thursday that it opposed what it said were the attempts of some civic groups to "drag the military into politics."
Boko Haram has staged many attacks in northeastern Nigeria over the years, a campaign of bombings and massacres that has intensified in recent times despite a strong military presence there. Since May 2013 there has been a state of emergency in three northeastern Nigerian states wracked by Boko Haram violence.
Boko Haram has killed more than 1,500 people this year. The militants, who want to impose Islamic Shariah law on Nigeria, abducted more than 300 girls from a boarding school in the northeastern town of Chibok. Fifty-three escaped but 276 remain captive. In a video seen by The Associated Press, Boko Haram's leader threatens to sell the girls into slavery.
The government of Borno state, where Chibok is located, on Thursday identified the girls who escaped, potentially subjecting the girls to stigma in this conservative society.
The government said in a statement received Friday that the girls it identified by name include those who fled the day they were kidnapped and those who escaped from Boko Haram camps days later. It did not explain the decision to name the girls.
Chibok residents staged a street protest Friday to press Borno's government to do more to find the missing girls.
Militants from Boko Haram are also believed to have carried out the bombing of a strategic bridge linking the town of Gamboru to the Borno state capital, Maiduguri, the headquarters of the Nigerian military offensive, a local government official confirmed Friday.
Gamboru was attacked on Monday by Boko Haram, leaving many dead. Estimates of the death toll from that attack ranged from 100 to as many as 300. Local security officials said on Friday that Boko Haram militants bombed the bridge as they retreated following the attack on Gamboru's main market, where at least 50 bodies have since been discovered from the debris of burned shops.
Communications with the remote town are difficult and it was not immediately possible to reconcile conflicting accounts of when the bridge was bombed. One account said Monday while another said Thursday.
Local traders in Gamboru said Friday that their businesses were suffering, with trailers and heavy trucks now stranded on either side of the damaged bridge.
"We are in trouble," said Gamboru resident Mamman Abu.