The clowns were found in bright costumes and makeup on a roadside Sunday in the city of Villahermosa, bearing signs of torture and a message accusing them of being army informers, their families said.

The Tabasco state attorney general's office said they were found with a message attributing the crime to the Zetas drug gang, which is known to be active in the area.

Police meanwhile found a female head wrapped in a jacket in a park in the Chihuahua town of Jimenez, in the most gruesome of 15 murders uncovered overnight, the state attorney general's office said.

Eleven of the deaths occurred in the border city of Ciudad Juarez, across from El Paso, Texas, which has Mexico's highest murder rate. More than 30,000 people have been killed in violence related to the drug trade across Mexico since December 2006, when the government launched a major military offensive against organized crime.