The decapitated heads of three suspected members of the Zetas drug cartel were found on the trunk of a car in eastern Mexican state of Veracruz, authorities said Thursday.
With them authorities found a note in which another cartel, Jalisco Nueva Generacion, apparently claimed responsibility.
The grisly discovery came in the state capital, the port city also called Veracruz, said a police official.
The note said: "This is going to happen to any filthy Z that goes around kidnapping and robbing innocent people," according to the police official.
The heads, with signs of torture, were found Wednesday night after police were advised by local people.
In late December five people were found decapitated in the western state of Michoacan, also along with a note from the Jalisco Nueva Generacion cartel, which is fighting for control of the state with rival drug gangs called the Knights Templar and La Familia Michoacana.
Veracruz is one of the Mexican states hardest hit by drug-related violence by cartels such as the Zetas, which resorts to abductions and extortion, as well as robbery and trafficking of undocumented migrants trying to reach the United States.
Also in December the remains of three women and four men were found in several clandestine graves on a beach in Veracruz. The state lies on the Gulf of Mexico and boasts Mexico's biggest commercial port.
In September of 2011, members of Jalisco Nueva Generacion claimed responsibility for the killing of 35 people. The bodies were found inside trucks parked outside a shopping mall in Boca del Río, a tourist area of Veracruz.
In the past seven years more than 77,000 people have died in drug-related violence in Mexico.