Nigeria's government has denied that militant Islamist group Boko Haram abducted 500 children from the north-eastern town of Damasak.

A former resident said on Tuesday that the militants had taken away about 500 boys when they fled the town earlier this month.

Government spokesman Mike Omeri said the number was lower, but he could not say exactly how many had been seized.

Regional forces recaptured Damasak, a trading town, earlier in March.

Mr Omeri said that the militants released some women and children when they fled the town, but not those "they had married in the period of occupation".

The militants were using them as "protection" and the government had ordered "full military intervention" to secure their release, he said.

Damasak is in Borno state near Niger's border and is about 200km (120 miles) from the state's main city of Maiduguri.

Damasak businessman Malam Ali, whose brother is among those missing, told the BBC Hausa Service on Tuesday that young boys had been put in a madrassa, or Islamic school, by Boko Haram when they took over the town at the end of last year.

Following the recapture of the town, those boys, numbering about 500, had not been accounted for, he said, while Reuters news agency quoted residents as saying more than 400 women and children had been abducted.

Chibok girls

BBC Nigeria correspondent Will Ross says the conflict has torn many families apart.

As towns have changed hands it has been impossible to work out how many people have been killed and how many are missing, he adds.

Last week, the decomposing bodies of more than 70 people were discovered under a bridge near Damasak.

Nigeria's military has still failed to free more than 200 girls abducted more than a year ago from Chibok, also in Borno state.

The abductions caused international outrage, and foreign governments promised to help Nigeria 's military find the girls.

Boko Haram leader Abubakar Shekau has said the girls have been married off.

The group has waged a six-year insurgency in Nigeria to create an Islamic state, killing thousands of people and capturing many towns and villages.

Regional forces launched an offensive about six weeks ago to regain territory ahead of delayed presidential and parliamentary elections, now due on Saturday.