Men stand next to the wreckage of a tractor-trailer set ablaze by members of a drug carte. Armed men shot at a Mexican army helicopter in the western state of Jalisco on Friday, killing three military personnel and injuring 12 others. (Stringer/Mexico/Reuters)

Gunmen shot down a Mexican military helicopter Friday in the western state of Jalisco, killing three soldiers, and set fire to buses, blocked roads, and attacked banks and gas stations in a sharp escalation of violence against the government.

In recent months, the New Generation drug cartel has been ratcheting up attacks against the government, including an ambush last month that killed 15 state police officers. State authorities have worried that the federal government has left them ill-equipped to deal with an ascendant cartel trafficking heroin and methamphetamines.

On Friday, the Mexican army announced Operation Jalisco to try to wrest control from the cartel. The helicopter was forced to make an emergency landing when it came under fire while patrolling a rural road near the Pacific coast, according to the Mexican army. At least 10 soldiers and two police officers were wounded in the incident.

“I lament the deaths of the members of the Mexican military in the fulfillment of their duty in Jalisco,” President Enrique Peña Nieto tweeted.

Firefighters work on a bus in Guadalajara, Mexico on Friday. More than a dozen vehicles were set on fire Friday across Guadalajara while a drug gang and authorities clashed in another part of the state. (Hector Guerrero/AFP/Getty Images)

In the state capital of Guadalajara, gunmen set vehicles ablaze and blocked roads in at least 20 areas, state officials said. Authorities declared a state of emergency and called on residents not to leave their homes. There were also reportedly fires in the coastal resort town of Puerto Vallarta.

Jalisco’s governor, Aristóteles Sandoval, told a news conference that clashes in the state have killed seven people and wounded 15. Authorities have also made 15 arrests, he said.

Security in Jalisco has been deteriorating steadily as the New Generation expands its reach.

Luis Carlos Nájera Gutiérrez de Velasco, the state’s attorney general, described the group as the “least vulnerable, least attacked” of the major drug gangs and said the federal government has not been doing enough to help the state. In an interview this week, he said that the cartel has expanded to more than 10 states in Mexico and that much of the heroin being seized at the U.S. border is smuggled by its members. The cartel has also gotten rich from the methamphetamine trade and by stealing gasoline from a pipeline that runs from Guanajuato state. “This group has gotten very strong,” he said.

“For many years, we have been fighting these criminal groups alone,” Nájera said. “We stated long ago the risks we have with this criminal group, and it appears it has not been a priority. We will keep fighting, with or without help.” After the deadly ambush, he said, “we believed this would make the federal government pay more attention, but we don’t see any difference.”

Part of the reason the New Generation has grown stronger is that leaders of rival gangs, such as the Knights Templar in Michoacan state, have been killed or captured.

Policemen detain a man on suspicion of being a member of a drug cartel in Guadalajara. (Stringer/Mexico/Reuters)

Nájera said one of the cartel’s main weapons is the ability to corrupt or threaten police and local officials. He said he and top officials constantly receive threats from the cartel. Earlier this month, gunmen tried to kill the state’s security commissioner, Alejandro Solorio. In the past, he said, the cartel focused more on its business activities than on displays of violence. But he said he fears that the recent attacks on security forces are a warning to authorities to stay out of the cartel’s way. “They want to work freely,” Nájera said. “We have to keep fighting this or any other criminal group, because if we stop fighting, there will come a time when we are so invaded that we won’t be able to do anything.”