Nigerian police have found rotting bodies, skeletons and people bound in chains in a house in Ibadan that has been dubbed the House of Horrors.
They said that emaciated people had also been found wandering in the grounds of the property, reports AFP.
Police raided the house after a group of people looking for a missing relative, who was a motorcycle taxi driver, found the property in an undeveloped part of the Soka community and discovered there were people trapped inside.
"When we got to the abandoned building in the Soka community of Ibadan yesterday (Saturday), we saw decomposed corpses, skeletons and skulls in the building and surrounding bushes," Oyo state police spokeswoman Olabisi Ilobanafor told AFP.
"Some seven malnourished human beings looking like living skeletons were also rescued in the bushes surrounding the building. One of them died on the spot while we were there," she said.
Ilobanafor said that a murder investigation had been launched and six suspects were arrested at the scene.
Ibadan is Nigeria's third largest city, and the capital of Oyo state.
In Nigeria, kidnapping victims are often killed in black magic ritual sacrifices or for their organs or body parts, which are sold on in the southern region of the country.
Corpses are often found abandoned on roadsides near the country's cities with parts of their bodies missing, including their eyes and genitals.
Nigeria's Vanguard newspaper last year reported that three dealers in body parts and kidnapped people had revealed a "price list", where a live person could be bought for about £150, a human head for £30 and genitalia for £36.
The Nigerian Tribune newspaper reported that about 15 people were found chained up in the property in Ibadan, and six guns and several cutlasses recovered from a neighbouring house.
Containers holding clothes, shoes, mobile phones and bank cards were found inside.
The Tribune claims that a woman held as a captive had been forced to deliver a baby at the property only the previous Friday. The child was then taken away from her.
The Nation newspaper reported that bodies had been dumped in shallow graves and dry wells.
One resident quoted by the Tribune said: "When I got there, I saw people who were like mad people but on a closer look, I saw that they were not really mad, but had gone through starvation. Some of them said they had been there for two years while others said seven months."