Police have discovered the remains of five men discarded along the highway between Monterrey and Reynosa, in northern Mexico

The bodies were naked, except for plastic bags. In other violence, gunmen clashed with soldiers in three separate incidents in the northern Mexican state of Tamaulipas, leaving 13 people dead. In the first, in San Fernando, gunmen opened fire on a group of soldiers as they were making their rounds. The soldiers responded in kind, leaving six people dead. The second incident, in Valle Hermoso, occurred when soldiers on patrol came under gunfire and they responded, leaving six people dead. In the third incident, in Nuevo Laredo, soldiers again came under attack and killed one of their assailants. A second man was arrested.The clashes are the latest in a string of violence fueled by the lucrative drug trade in Mexico. According to the Mexican government, there have been more than 34,600 drug-related deaths since December 2006.