MEXICO CITY -- A drug cartel that unleashed a wave of attacks in the western Mexican state of Jalisco used a rocket-propelled grenade to force down a military helicopter, a security official said Monday.

National Security Commissioner Monte Alejandro Rubido told the Televisa network that the Friday attack showed the Jalisco New Generation cartel had significant firepower. Previously, the government had said only that attackers had fired upon the helicopter without describing the weapon.

Later, in an interview with Radio Formula, Rubido said "it is the first time that they've shot this kind of helicopter."

Authorities have known that cartels possess such weapons for years.

"Very likely they (criminal organizations) have already tried to use them against helicopters," said Alejandro Hope, a security expert and former official from Mexico's intelligence service. "What's new is that now they did it."

At least 15 people were killed and 19 injured in a series of attacks in Jalisco on Friday, during which 11 banks and five gas stations were burned.

Rubido said three soldiers initially reported as missing from the helicopter have been confirmed as dead, raising to six the number of people killed in that attack. A state police officer was also killed in a separate incident. Eight suspected gunmen were also killed, Rubido said.

The helicopter was forced to make an emergency landing after it was fired upon by gunmen travelling in a convoy early Friday, according to authorities. The helicopter, which carried 18 people, was participating in the start of "Operation Jalisco," a federal offensive targeting leaders of the Jalisco New Generation cartel.

Last month, the cartel killed 15 people when it ambushed a convoy of state police.

The cartel has grown stronger in recent years as rivals such as the Knights Templar and Zetas weakened. It emerged from another former gang and later operated as a faction of Ignacio "Nacho" Coronel, a leader of the Sinaloa cartel, who died in a federal operation in July 2010.

After that, the cartel began to operate independently. The U.S. State department considers it one of Mexico's most powerful drug trafficking cartels.

Nineteen people were arrested Friday, but Rubido said that none was a leader of the cartel.