MEXICO CITY Armed gunmen burst into a drug rehabilitation clinic in northern Mexico late on Sunday, leaving 11 people dead and at least 8 wounded almost a year to the day after a similar fatal attack nearby.
State police said the assault, part of a drug war widely estimated to have claimed more than 55,000 lives in less than six years, took place in the outskirts of Torreon, an industrial city in the border state of Coahuila. They could not immediately give more details.
In June last year, 13 people were killed at a rehab center in the same city.
One worker at a drug recovery center in the border town of Ciudad Juarez said recently that traffickers sometimes seek shelter at the centers, endangering other patients when their rivals seek them out.
Mexico's drug cartels have mainly focused on U.S. narcotics consumers but numbers of home-grown users are increasing, creating new turf wars that threaten to further stretch the country's security forces.
Similar attacks have happened in other violent border cities.
In a 2010, two dozen men armed with automatic weapons stormed the "Faith and Life" drug clinic in the city of Chihuahua and killed 19 patients all under the age of 25.
With a presidential election less than a month away, a spate of gruesome drug-related murders - including the dumping last month of 49 decapitated bodies on a highway outside the major city of Monterrey - is shining an unwelcome spotlight on the country's security situation.
President Felipe Calderon is barred by law from running for another term, and his conservative party looks unlikely to win endorsement from an electorate increasingly disenchanted with his failure to get to grips with the spiraling violence.
The party's candidate, Josefina Vazquez Mota, is lagging in third place in the polls.
Opposition frontrunner Enrique Pena Nieto, from the Institutional Revolutionary Party, says Calderon' army-backed drug war has failed and promises to change the country's course if he wins the July 1 vote.
Pena Nieto is not offering a radical departure from Calderon's policies but polls show voters believe he will do a better job of curbing violence.
He proposes creating a military police force to fight drug gangs and wants to carry forward reforms to the justice system that aim to professionalize criminal investigators and courts.
(Reporting by Mica Rosenberg; Editing by John Stonestreet)