Nigeria’s Chief of Defence says they know where Islamic militants are holding nearly 300 kidnapped schoolgirls but the military cannot use force to go in and free them.

Alex Barde says “we can’t go and kill our girls in the name of trying to get them back.”

The girls were taken from their school six weeks ago by Boko Haram extremists.

Most officials think any raid to rescue them would be too dangerous and probably not worth the risk that the girls would be killed by their captors – an Islamist group that has shown ruthlessness in killing civilians.

Since the girls were captured at least 470 civilians in various regions have been killed by Boko Haram, which says it is fighting to establish an Islamic state in religiously mixed Nigeria.