Gunmen in the Mexican city of Tijuana have shot dead 13 people at a drug rehabilitation center, say police

The attack appeared to be connected to the long-running violent conflict between drugs gangs in the the country, in which thousands have been killed. Recently, police in Tijuana destroyed 134 tonnes of cannabis - the largest drugs haul ever seized in the country. The drugs, with an estimated street value of at least $340m, had been wrapped in 15,000 separate packages. Police in Tijuana, just over the border from San Diego, California, said the latest killings happened when an armed gang burst into the Camino drug treatment center in the city. They lined the victims up and shot them with high-powered weapons. Drugs rehabilitation centers have been attacked by gunmen before - observers say the gangs accuse the clinics of protecting rival dealers. Police also believe drug cartels use the clinics to recruit hit-men and smugglers, threatening to kill those who fail to co-operate.