Four inmates were killed and eight seriously injured during a riot over water supplies at a prison in Ivory Coast's main city Abidjan on Tuesday, the West African country's chief prison administrator said. "There are four confirmed dead and eight were injured. Some prisoners escaped but we don't know how many yet," prison administrator Francois Guei said. "Two were killed by bullets and it seems two were killed with machetes or knives," he said. Rioting broke out early on Tuesday at the main MACA prison, where water supplies had been cut for several days, and continued until security forces brought the violence under control, shooting dead two prisoners as they did so, Guei said. The prison, which was built more than two decades ago in Abidjan's Yopougon suburb, holds 5,400 inmates but has an official capacity of just 1,500, Guei said. Ivory Coast has been split in two since war broke out in the world's top cocoa grower in 2002. The rebels holding the north of the country withdrew from a long-delayed disarmament process last week and have warned that the war could start again soon.