Four decapitated bodies have been found hanging from a bridge in Mexico's Sinaloa state, part of a surge of violence that claimed the lives of 20 people in less than a day.

Violence has soared in Sinaloa since the capture in the U.S. of cartel co-founder Ismael "El Mayo" Zambada almost a year ago.

Prosecutors in northern Mexico’s Sinaloa state are investigating the discovery of 20 male bodies with gunshot wounds – including five that were decapitated – on a bridge over a federal highway.