MEXICO CITY (AP) — President Felipe Calderon insisted Friday that few innocent civilians have fallen victim to Mexico's bloody drug war, saying nearly all those killed are people tied to cartels wrestling for power.

Speaking during a tourism conference, Calderon said criminals constitute more than 90 percent of drug war's death toll, which stands at nearly 23,000 in just over three years.

Calderon said police officers and soldiers make up less than 5 percent of deaths and bystanders or other innocents even less.

"But even so, my friends, I recognize that it's a real problem," Calderon said of the drug violence.

"We are fighting it with firmness and we are making progress with our goal," he added.

Calderon's comments came two days after a gunbattle in broad daylight killed six people and wounded five on the main boulevard of Acapulco's tourist zone. Among the dead were a mother and her 8-year-old child. A federal police officer and another bystander also were killed. Federal police have arrested 26-year-old Ernesto Antonio Rocha Reyes, an alleged hit man authorities say carried out the attack with a high-powered assault rifle.

On Friday, four police officers were shot to death in the border state of Tamaulipas.

In Cuernavaca, a city near Mexico's capital, authorities said they found three bags stuffed with hacked-up bodies dumped in a busy street, accompanied by a message that tied the killings to a drug cartel. Police said the number of bodies had not been determined.

Cuernavaca has seen a spike in violence since Mexican marines killed drug kingpin Arturo Beltran Leyva during a December shootout at an upscale apartment complex in the city. Authorities say Beltran Leyva's death triggered a battle for control of his cartel.

The city of 350,000 has been subjected to a wave of fear as bodies continue to turn up, and messages signed by the "Resistance" or "The Southern Pacific Cartel" turned up on the Internet.

The group is believed to be the remnants of the Beltran-Leyva cartel, who are fighting former cartel colleague Edgar Valdez Villarreal, a U.S.-born enforcer known as "La Barbie."

The messages caution residents not to go out at night and avoid driving the kind of pickups and SUVs favored by drug traffickers, to avoid becoming the target of rival gangs.

Graduate student Zuzuanta Garfias said nighttime classes in quality control-management at her private university were canceled this week, because of safety concerns.

"They told us to go home, and that is what I am going to do," said Garfias.

While universities have not been particularly targeted by drug violence, Mexico was shocked when two university students were killed in the crossfire of a shootout between gunmen and soldiers outside the gates of their campus on March 19 in the northern city of Monterrey.

Elsewhere Friday, state police in the western state of Michoacan said the chief of the city public safety department in Ciudad Hidalgo had been shot to death along with his driver. A note found in the car along with the bodies read: "This is for collecting and not living up to it."

The slain official, Rafael Munos Rojas, a former federal police officer, took over as the top police official in Ciudad Hidalgo after the city's mayor was accused of aiding a drug cartel. The mayor has since been released and returned to office.

Also Friday, federal authorities announced they seized more three tons of pseudoephedrine in a shipment that arrived at the Gulf coast port of Veracruz from India. Pseudoephedrine is a precursor chemical used to manufacture methamphetamines.

An estimated 22,700 people have been killed in Mexico's drug war since December 2006, when a U.S.-backed military crackdown on the cartels began, the government said earlier this week. Its report said more than 9,630 people were killed in 2009, making it the deadliest year in the drug war so far.

Calderon said the instances where innocent people are caught in crossfire between police and drug criminals are few, "but they are very painful for us."

Calderon acknowledged that Mexico has a high homicide rate, putting it about 11.6 for every 100,000 residents, but he insisted it is lower than other popular tourist destinations like Jamaica or the Dominican Republic.

Calderon said Mexico has an "image problem" but the country is committed to being a safe destination for tourists.

"We have to work on the perception and image of Mexico," he said.