Nigeria’s army says it has located hundreds of schools girls abducted by Boko Haram last month but won’t use force to free them.
Air Chief Marshal Alex Badeh, Nigeria's Chief of Defense Staff, said on Monday that any potential armed rescue operation was fraught with danger as the 223 girls still held hostage could be caught in the crossfire.
Boko Haram fighters kidnapped 276 girls from the remote northeastern town of Chibok on April 14, leading to global outrage.
"The good news for the girls is that we know where they are but we cannot tell you," Badeh told reporters in the capital Abuja, as the hostage crisis entered its seventh week.
"We can't go and kill our girls in the name of trying to get them back," he said.
Earlier, a deal to release some of the girls was reportedly close but was called off by the government.
The BBC's Will Ross in Abuja says an intermediary met leaders of the Islamist group and visited the place where they were being held.
He says agreement was almost reached to release 50 of the girls in exchange for the release of 100 Boko Haram prisoners.
But the Nigerian government pulled out of the deal after President Goodluck Jonathan attended a conference on the crisis in Paris. The reasons for the withdrawal are unclear.Nigeria's government is under pressure to do more to tackle the group and bring about the girls' release.
Thousands of people have died since Boko Haram began a violent campaign against the Nigerian government in 2009 and in the subsequent security crackdown.
Chief of Defence Staff Air Marshal Alex Badeh said on Monday that "the good news for the parents of the girls is that we know where they are" but said he couldn't reveal the location.
"But where they are held, can we go there with force? We can't kill our girls in the name of trying to get them back," he added.
Mr Badeh was addressing demonstrators who had marched to the Ministry of Defence in Abuja to protest against the government's response.
"Nobody should come and say the Nigerian military does not know what it's doing," he told the crowd. "We know what we are doing."
"The president is solidly behind us. The president has empowered us to do the work," Mr Badeh said.