Boko Haram militants have issued an ominous warning to the parents of abducted Nigerian schoolgirls after releasing them in the town where they were taken a month ago.

A witness in the town of Dapchi said the fighters told residents they had returned the girls “out of pity”.

“And don’t ever put your daughters in school again,” they warned.

Boko Haram translates as “Western education is forbidden” in the local Hausa language.

It was not immediately clear how many of the 110 girls have been freed.

In 2014, the group abducted 276 schoolgirls from Chibok, and about 100 of them have never returned to their families.

The release of the girls comes a day after an Amnesty International report accused the Nigerian military of failing to heed warnings of the attack.

Nigeria’s military dismissed the report as an “outright falsehood”.

Amnesty International cited sources including security officials and witnesses who said military and police received at least five calls in the hours before the attack.

The rights group said no lessons had been learned from Chibok and urged Nigeria’s government to make public its investigation into the new attack in Dapchi.

Nigeria’s acting director of defence information John Agim said no security force was informed of the mass abduction.