Guards at a maximum security prison in Cameroon's port city of Douala shot dead 16 inmates during an attempted break-out, state radio said on Monday. It said the prisoners made the escape bid from the New Bell prison late on Sunday, cutting off electricity and then opening fire on warders with two automatic rifles. "The warders on guard ... responded with fire for fire. By the time the sustained gunfire died down, 16 inmates were killed and three others sustained serious injuries," the radio said. Two of the prison guards were slightly hurt, Reuters reported.