A man and his three wives have been arrested in north-western Nigeria on suspicion of the long-term detention and torture of their 12-year-old son.

The boy was found on Sunday among goats and hens inside a makeshift structure where he was tied to a wooden pillar.

After a tip-off a team of human rights lawyers and police said they found him barely able to stand on his feet, and looking malnourished.

Yet the boy’s family including 17 siblings was living in a comfortable home, according to the head of the Kebbi state Human Rights Commission Hamza Attahiru Wala, who led the rescue team.

The boy has been taken to an intensive care unit at a hospital in Birnin Kebbi.

Investigations are under way, police say, and the parents face formal charges later this week.