Two severed heads have been found in the Mexican resort town of Acapulco, the latest in what police suspect is a brutal round of drug-related killings.
Grisly discoveries have become commonplace in Acapulco recently
A note was found alongside the victims reading: "So that you learn respect".
A pair of decapitated bodies were also found elsewhere in Acapulco, with one other head found a day earlier outside Acapulco's city hall.
Police believe Acapulco's rising murder rate is fuelled by a group of former soldiers now working for a drug cartel.
Earlier this year a severed head washed up on the beach in the middle of Acapulco's tourism district.
The latest discoveries bring to six the numbers of severed heads found in the Pacific coast city during 2006.
The heads were found outside the Guerrero state finance department, where the heads of two police officers were found in April.
Those heads, and the bodies that were also discovered, were also accompanied by similarly threatening notes.
The notes have been signed with the initial "Z", believed by the authorities to refer to "Los Zetas", a group of ex-elite soldiers recruited by the Gulf drug cartel and now involved in a battle for control of drug supply routes into the US.
Candidates in Sunday's presidential election in Mexico have pledged tougher action against cartels as drug-related violence has soared across the country in recent months.