Mexico City: Gunmen barged into a bar in central Mexico early Wednesday and tossed five human heads on the dance floor after ordering customers to get down on the floor a chilling show of brutality in a nation plagued by growing drug violence.

The internet site of the Mexican newspaper Reforma carried a gruesome photo of heads scattered across a white tile floor smeared with blood. Next to the heads was a note written on a piece of cardboard reading: "The family doesn't kill for money. It doesn't kill women. It doesn't kill innocent people, only those who deserve to die. Everyone knows that. This is divine justice."

A spokesman for the federal Attorney General's Office in Michoacan state confirmed the incident and said no arrests had been made. He said he was not authorised to give his name or more details. Other officials in the office were in a meeting and unavailable for comment.

Heavily armed men shot their guns in the air as they entered the bar in the city of Uruapan at about 1.30am, Reforma and the Mexican newspaper Milenio reported.

They ordered patrons to the ground before tossing the heads in plastic bags on to the centre of the dance floor.

Police were still trying to identify the victims, according to reports. Last week, officials found the decapitated body of a man in the town of Tepalcatepec. But authorities had not yet determined if his head was among the five, the newspapers reported.

The arrest of major cartel leaders has sparked an increasingly brutal and ruthless drug war in Mexico as gangs battle for control of lucrative routes.

So far this year, at least six human heads of police and rival drug smugglers have been found in the Pacific resort of Acapulco. One washed up on a popular beach in the tourist zone, and the rest have been dumped in front of government offices.

In the past few months, heads have also been found in other states plagued by drug violence, including the border states of Baja California and Nuevo Leon.

President-elect Felipe Calderon has pledged to crack down on drug violence and make public security a top priority.

Calderon is from Michoacan state, but there were no immediate indications the brutal display was aimed at sending him a message.