Ten people were killed in separate violent incidents between Friday night and Saturday morning in the northern Mexican city Torreon, Coahuila state, local police said Saturday.

Five of the ten victims had been decapitated, and the heads were found one after another in various parts of the city since Friday night, officials said, adding that they were still searching for the bodies.

Policemen found threatening messages at every crime scene, which suggested the slayings were organized crimes between local drug gangs.

The other five people were killed Saturday morning, four by gunshots and one was stabbed to death.

Local authorities responded to the crimes by tightening security throughout the city.

More than 45,000 people have been killed in drug-related violence in the Latin American country since President Felipe Calderon launched the nationwide "war against organized crime" after taking office in 2006.