Organized-crime slayings in Mexico more than doubled in the first 11 months of 2008, as powerful drug cartels fought increasingly bloody battles for control of trafficking routes and territory, the government said Monday.

Attorney General Eduardo Medina Mora said gangland killings rose by 117 percent to 5,376 as compared to the first 11 months of 2007, when there were 2,477 slayings. The government had previously not provided a total number for such killings and the figure came days after Washington began releasing funds from an anti-drug aid package.

Underscoring the brutality of the conflict, authorities on Monday said at least 18 people were killed in a single day in southern Guerrero state and that two human heads were left in buckets outside the governor's office.

Medina Mora said the spike in "homicides related to organized crime" was largely caused by an internal falling out between former allies in the Sinaloa cartel, Mexico's most powerful drug gang.

The wave of killings, massacres and beheadings began at the start of 2008 when the Beltran-Leyva gang split from the main wing of the cartel led by Joaquin "El Chapo" Guzman setting off battles between rival factions, the attorney general told reporters.

The increasingly gruesome slayings also come amid a massive government offensive against Mexico's drug cartels in which President Felipe Calderon has sent tens of thousands of soldiers to states plagued by drug gangs. Since Calderon took office on Dec. 1, 2006, a total of 8,150 people have died in organized-crime slayings.

Other contributing factors include long-standing disputes for control of drug trafficking routes, increased street-level drug dealing and leadership disputes following the arrest of some cartel lieutenants, law enforcement officials say.

Mexican law enforcement has also been hit by the biggest corruption scandal in a decade in recent months, as more than a dozen high-ranking officials in police and prosecutors' offices have been detained or charged for allegedly passing information to the cartels.

Medina Mora said the law enforcement cleanup, known as "Operation Clean House," had not affected U.S. confidence in Mexico's ability to fight drug traffickers, adding it had done "rather the opposite."

"This is not only not affecting the confidence and capacity to work together, it has even increased the level of cooperation and confidence," Medina Mora said.

Last week, the U.S. government released $197 million, the first installment of a $400 million aid package to support Mexico's police and soldiers in their fight against drug cartels.

On Monday, the Guerrero Public Safety Department said in a news release that 10 suspected traffickers and a soldier were killed in two gunbattles Sunday in the town of Arcelia. Authorities also found the bodies of three men who had been shot to death near Acapulco. Two other men were beheaded in Guerrero and two more men where shot to death.

In neighboring Michoacan state, the bodies of three men who had been missing since Thursday were found near the town of Zitacuaro. All three had been tortured and shot in the head, state investigators said in a statement.

Police in the northeast city of Monterrey said 10 banners alleging police corruption and federal protection of drug cartels were found Monday.

The banners, painted on white sheets in black and red ink, appeared outside various locations in Monterrey including the city's cathedral, a hospital and the town hall of San Nicolas, a Monterrey suburb.

Several of the messages were addressed to Calderon and alleged Public Safety Secretary Genaro Garcia Luna is helping the Sinaloa drug cartel. Garcia Luna has rejected those allegations.