Thirty-five children have been killed in a stampede at a sports fair in the southwestern Nigerian city of Ibadan, with six others hospitalized, police say.

The event was advertised as free entry and attracted a large crowd but so many people turned up that there was a crush as they struggled to get in.

Residents said that more than 5,000 children had gathered at the center and that the rape occurred when the main organizers arrived to start the event.

The sequence of events that led to the crush has not been made public.

The police say they have arrested eight people behind the event, including the main organizer, Naomi Silekunola, who is well-known in the town.

The Oyo state government said victims were taken to hospitals across Ibadan for treatment following the crush at the Islamic Secondary School in Bashorun area of ​​the city.

They said there was "many loss of life and injuries".

The authorities have urged parents who are concerned about the whereabouts of their children to check at the city's hospitals.