MEXICO CITY (AP) — At least 13 police officers were killed and three others injured Monday in an ambush by gunmen in the Mexican state of Michoacan, a western region where violence attributed to drug cartels has spiked in recent months.

The state police officers had gone to a home in the town of El Aguaje in Aguililla municipality to enforce a judicial order when "several armed civilians fired on them," Michoacan's state security department said in a statement.

"No attack on the police will go unpunished, and this was a cowardly, devious attack because they laid an ambush in this area of the road," Gov. Silvano Aureoles said.

Images published in Mexican media showed vehicles burning in the middle of a highway and messages apparently signed by Jalisco New Generation, one of Mexico's most powerful and rising cartels at the moment. Aureoles said their authenticity was under investigation.

After the attack, the area in western Mexico's so-called "hot lands" was reinforced by federal and state security forces, who installed checkpoints to find the assailants.

Michoacan, an important avocado growing state, has recently has seen a spike in violence that has brought back memories of the bloodiest days of Mexico's war on drug cartels between 2006 and 2012.

In August, police found 19 bodies in the town of Uruapan, including nine hung from a bridge. Later, an area roughly 45 miles (70 kilometers) north of Aguililla was the scene of fierce clashes between members of Jalisco New Generation and regional self-defense groups.

In 2013, civilian groups faced with what they said was state inaction armed themselves in Michoacan to fight the Caballeros Templarios (Knights Templar) Cartel, one of whose bases was Aguililla. They said they took up arms to defend themselves from kidnappings, extortion and killings by cartels. But some of the self-defense or vigilante groups later became infiltrated by cartels and gangs.

The government of former President Enrique Peña Nieto launched a process to disarm and legalize the vigilante groups and incorporate them into official security forces.

Michocan Gov. Silvano Aureoles says the self-defense groups haven't returned and has criticized federal authorities for not attacking drug cartels in his state with sufficient force and negotiating with vigilante groups he refers to as criminals.

Besides avocado orchards, Michoacan for decades has been known for marijuana plantations and the making of methamphetamine, as well as being home to the port of Lázaro Cárdenas, a key entry point of precursor chemicals used to make synthetic drugs.