At least 20 of the 80 people abducted by Boko Haram in Cameroon have been freed, according to the country's defence ministry.

The Islamist extremists kidnapped 30 adults and 50 young children after they raided two villages in the northern region of Tourou.

It is not clear at this stage who has been released following an offensive carried out be security forces against the terror group.

It is believed to be the biggest kidnapping by Boko Haram outside Nigeria.

"They torched houses and left with around 60 people. Most of these people were women and children," a police officer told AFP.