Nigeria's militant Islamist group Boko Haram has forced abducted women and girls to go to the front line to help fight the military, a new report says.
The group has taken more than 500 women and girls hostage since it began its insurgency in 2009, the Human Rights Watch (HRW) report adds.
Suspected militants seized about 30 children on Thursday, despite government claims of a truce.
Boko Haram has declared a caliphate in areas it controls in the north-east.
The group had intensified abductions since May 2013, when Nigeria's government imposed a state of emergency in the three states where Boko Haram was most active - Borno, Yobe and Adamawa, HRW said.
'Shaking with horror'
The New-York based group estimates that more than 4,000 civilians have been killed in more than 192 attacks since May 2013 in the north-eastern and in the capital, Abuja.
At least 2,053 civilians were killed by Boko Haram in the first half of 2014, it says.