Guadalajara, Mexico: Gunmen forced down a military helicopter in western Mexico on Friday killing three troops, as deadly violence erupted across Jalisco state during a new operation to capture drug cartel leaders.

Seven people were killed across Jalisco, including the three soldiers, two gang suspects, a state police officer and a civilian, the local government said, and more than a dozen wounded.

The attack on the Cougar helicopter in the southwestern part of the state came as vehicles were set on fire or used as roadblocks at numerous points in the state, including more than a dozen in Guadalajara, Mexico’s second biggest city, where residents were told to stay indoors.

The mayhem — which also saw 15 people across the state detained and banks and gasoline stations set ablaze — erupted on the day that the military and federal police launched Operation Jalisco to crack down on the Jalisco New Generation Drug Cartel.

Officials say the New Generation cartel, led by Nemesio Oseguera, alias “El Mencho,” has grown so powerful that it has produced its own assault rifles in makeshift gun assembly shops and has forged ties with crime groups across the globe.

“This [violence] is a reaction to an operation to detain leaders of this cartel,” Governor Aristoteles Sandoval told reporters, without identifying the gang by its name.

The military helicopter was taking part in the operation when it spotted carloads of gunmen on a road between the towns of Casimiro Castillo and Villa Purificacion, the defence ministry said.

“[The gunmen] attacked the military personnel with shots from firearms, hitting the Cougar helicopter, which conducted an emergency landing,” the defence ministry said in a statement.

Another three soldiers on the helicopter were missing. The location of the helicopter attack was near the town of Autlan, where a state police officer died in a clash with gang suspects.

The New Generation cartel has violently defied the authorities this year, killing 20 police officers in two ambushes in March and April.

Starting at around 9.45am in Guadalajara, buses and trucks were torched in at least a dozen streets. The fires were put out hours later.

Such tactics have been used by gangs in Mexico to try to thwart police and military operations.

‘Remain calm’

Authorities urged residents of Guadalajara to stay indoors. No shoot-outs were reported in the city, according to the state government.

“Remain calm. If you have any reason to leave your house, don’t go out,” the Jalisco state prosecutor’s office said on Twitter. Before the violence erupted, the government announced the launch of Operation Jalisco, which includes the navy, the army, the federal police and the attorney general’s office “to guarantee the security of citizens and reduce crime.”

The New Generation is a rising power of Mexico’s underworld that had been overshadowed until now by other groups such as the Sinaloa, Zetas, Gulf and Knights Templar cartels.

The gang has even recruited military deserters, including foreign ones, security officials say.

The cartel has drawn the attention of the US government, which has funded Mexico’s battle against drug cartels by providing equipment, training and intelligence.

Last month, the US Treasury Department slapped financial sanctions against the New Generation and its shadowy boss, Oseguera, as well as its allies, the Los Cuinis cartel.

The gang has expanded beyond Jalisco into neighbouring Michoacan and Colima states, while forging ties with other criminal organisations in the United States, Latin America, Africa, Europe and Asia, according to the US Treasury.