About a dozen hooded gunmen burst into a Mexican rehabilitation clinic near the U.S. border on Wednesday, lining up patients before killing 17 of them, Reuters reported.
Drug gangs have targeted rehab clinics in the manufacturing city of Ciudad Juarez across from El Paso, Texas, accusing them of protecting dealers from rival gangs.
The attack was one of the deadliest in President Felipe Calderon's three-year war against drug cartels, despite the presence of 10,000 troops and federal police in Ciudad Juarez who constantly patrol the city's streets.
The suspected hitmen stormed their way into the drug and alcohol rehab clinic in Ciudad Juarez and forced patients into a line in a corridor before shooting them, the army and the El Diario newspaper said.
"Armed men shot at about 20 people, killing 17 of them and injuring three," said army spokesman Enrique Torres.
In a separate attack on Wednesday, gunmen killed the deputy police chief in Calderon's home state of Michoacan in western Mexico.
Jose Manuel Revueltas, appointed just two weeks ago, was intercepted by heavily armed men in two vehicles as he drove down a busy avenue in the state capital, Morelia, a few blocks from police headquarters, police said.
Revueltas, 38, and his two bodyguards died in the intense gunfire that also killed a man traveling on a bus.
Revueltas was a close aide of Michoacan's leftist governor, Leonel Godoy. Calderon has placed a heavy military presence in the state.
Calderon has staked his presidency on crushing the cartels whose brazen fight for control of smuggling routes into the United States worries Washington and has killed more than 13,000 people since late 2006.
U.S. President Barack Obama has pledged full support for Calderon's drug war but the $1.4 billion promised to Mexico in 2007 to help fight the powerful cartels is only trickling in, with $214 million so far released for equipment and training.