DAPCHI, Nigeria (Reuters) Islamist militants drove scores of kidnapped Nigerian schoolgirls back into the town where they had been captured a month ago and abruptly set them free on Wednesday.

The captors gave no reason for their release, but Nigeria denied that a ransom had been paid. Several of the girls said some of their friends had died in captivity and one was still being held.

The fighters from the Boko Haram group, some shouting God is greatest, drove the girls back into the northeast town of Dapchi in a line of trucks in the morning, dropped them off then left, witnesses told Reuters.

I dont know why they brought us back but they said because we are children of Muslims, one of the freed girls, Khadija Grema, told Reuters.

Aliyu Maina, reunited with his 13-year-old daughter, said the fighters stopped and blocked the road, they didnt talk to anybody, they didnt greet anybody.

They said people should make space for people to recognise their children and I got my child.

Boko Haram has waged a nine-year insurgency in northeast Nigeria and neighbouring states that has seen tens of thousands of people killed, more than 2 million displaced and thousands abducted. A 2015 military campaign drove the group from most territory it controlled, but much of the area remains beyond government rule, and insurgents still stage attacks from strongholds near Lake Chad.

The kidnapping of 110 girls aged 11-19 on Feb. 19 from Dapchi was the biggest mass abduction since Boko Haram took more than 270 schoolgirls from the town of Chibok in 2014 a case that triggered international outrage.

Dapchi residents said more than 100 girls had returned on Wednesday.