A group of hitmen sprayed four cars with bullets on a busy street in the city of Guamuchil in the early hours of Sunday, killing five young men and three female minors, a police source told Reuters.

In an earlier attack on Saturday, six other armed men caused pandemonium in the Pacific port city of Mazatlan by taking refuge in a shopping mall to escape security forces after they shot dead local police chief Sixto Escobedo when he resisted their attempt to kidnap him.

The attackers, dressed in police uniforms, took some 40 people hostage in a restaurant inside the mall while they negotiated their escape with police.

Drug gang killings in Mexico have soared to unprecedented levels, with some 1,700 people dead so far this year, as an army-led crackdown intensifies turf wars between rival gangs, whose hitmen are increasingly taking their battles public with daylight shootouts in busy streets.

President Felipe Calderón began his crackdown in late 2006 but opinion polls show many Mexicans worry he is failing to gain the upper hand on cartels, who have grown bold enough to post threats or recruiting advertisements on street banners.

Hitmen, who are known to sometimes don police gear, often dump bodies with torture marks or severed heads in public, and while the vast majority of the victims are drug gang members, a few dozen civilians have been killed in street battles.

It was unclear if Sunday's victims had links to drug gangs, who have been known to target rival gangs' family members.

“They killed three girls and five male youths,” a local police source in Guamuchil said. Two others were injured.

Sinaloa state in northwestern Mexico is one of the areas most affected by drug violence and is home to Mexico's most-wanted drug lord, Joaquin “Shorty” Guzman.

Images on Mexican online media Sunday, some captured by witnesses on their cell phones, showed frantic shoppers rushing away from the mall in Mazatlan and screaming employees in the food mall seeking shelter as gun shots ring out.

“The alleged delinquents took hostages at a restaurant for several hours. There was a negotiation in which they got a vehicle for their exit. They took (two) hostages with them, then released them and escaped,” a spokesman for the Sinaloa government told Reuters Sunday.

Local media said Escobedo, who was shot when he refused to get in the gunmen's car, was a local police commander.

More than 500 policemen, including a handful of senior commanders, have been killed since Calderón's crackdown began.

(Editing by Catherine Bremer, Editing by Anthony Boadle)