TORREON - To cries of "Kill them all!" gunmen opened fire at a weekend birthday party here, mowing down at least 17 people in another attack that laid bare the brutality of Mexico`s long-running drug war.

A dozen people were also wounded as the killers sprayed more than 200 bullets indiscriminately at the private celebration outside Torreon, an industrial city in the northern state of Coahuila.

Sunday`s attack brought the number of victims across the country, which has been blighted by drug-related violence since President Felipe Calderon launched a 2006 crackdown on the cartels, to at least 57 just in the past weekend.

The attack began early in the morning when the murder squad arrived at a popular party hall in the usually calm suburb of Torreon aboard eight SUVs, said Fernando Olivas, a Coahuila state government official.

"A heavily armed hit squad came and cried `Kill them all!` and they started shooting," a Coahuila police source told AFP, citing a witness. Most of those gunned down were in their 20s and 30s.

Investigators found more than 200 shell casings, mostly from bullets fired by AK-47 automatic rifles, which are widely used by Mexican drug gangs.

Police said they have not identified the shooters nor do they have a motive for the crime.

Mexico`s drug war sees daily killings as rival gangs battle to control routes for smuggling cocaine from South America and other narcotics into the lucrative US market, and fight the security forces that try to clamp down on the cartels.

Some 9,000 people were killed in Mexican drug violence in 2009 -- and in less than six months this year some 7,000 people have been already been killed, according to government figures.

Ground zero for the violence is Ciudad Juarez on the US-Mexico border, which saw some 2,660 murders in 2009 alone -- more than seven a day on average.

Located some 400 kilometers (250 miles) south of the US border at a key intersection for two major highways, Torreon has seen a spike in drug-related violence recently.

This latest slaughter was reminiscent of a similar attack in late January when hitmen working for a drug gang opened fire and killed 16 young partygoers in Ciudad Juarez.

In that attack, some 15 gunmen opened fire on a house party packed with teenagers, most of whom were high school or college students. Some were shot outside the dwelling, others gunned down as they tried to flee.

Almost at the same time but in Torreon, 10 people were killed when gunmen rolled up in a trio of Hummers and opened fire on a crowd inside a bar.

The recent wave of violence includes a car bombing in Ciudad Juarez on Thursday that killed four and wounded 11.

Ciudad Juarez Mayor Jose Reyes said that gang members set a trap using a wounded person dressed as a municipal police officer to lure federal police into a main intersection before the car bomb detonated.

Nearly 25,000 people have been killed since December 2006, when right-wing president Calderon made shattering the drug cartels a national priority and launched a massive crackdown.

The death toll however continues to rise, even though Calderon has deployed some 50,000 soldiers across the country to strengthen local police forces.

BDST: 1239 HRS, July 19, 2010