New Delhi, Feb. 23 -- The Mexican army killed Nemesio Ruben Oseguera Cervantes or El Mencho, leader of the Jalisco New Generation Cartel (CJNG), on Sunday, dealing a major blow to what had grown into Mexico's most dominant drug cartel and sparking unrest across large parts of the country.

In response, cartel members set vehicles on fire and used them to block highways in nearly a dozen states, sending thick smoke into the air. The capital of Jalisco, Guadalajara, became largely deserted Sunday night as residents stayed indoors, and classes were suspended in several regions on Monday.

According to the Defense Department, Oseguera Cervantes was injured during a military operation aimed at capturing him in Tapalpa, roughly two hours southw...