Mexican Federal agents are taken to the municipality of Lazaro Cardenas in Michoacan state, Mexico, after being wounded in an ambush by alleged drug traffickers in the village of Pichilinguillo, on July 24, 2013. (EPA)

Last week, Mexican authorities were celebrating the capture of one of the country’s most notorious drug lords.

This week, they are facing a stunning escalation of cartel-related violence in an entirely different region — a sobering reminder that the grinding battle here against organized crime is being fought on multiple fronts.

In the past three days, gunmen in the convulsive western state of Michoacan have staged eight guerrilla-style ambushes on Mexican federal police convoys, killing four officers and wounding at least 15.

Open combat involving government security forces, criminal gangs and the local militias that have emerged to fight them have left at least 42 people dead in the past week in Michoacan, according to tallies by Mexico’s Reforma newspaper. Mexican officials said they are sending an additional 2,000 soldiers and police officers to prevent the violence from spiraling further out of control.

In a speech Thursday at Mexico’s naval academy, President Enrique Peña Nieto said government security forces in Michoacan would not relent in their campaign to vanquish the state’s gangsters and restore “peace and tranquility.”

“Michoacan has and will have the full support of the government to uphold the rule of law in every corner of its territory,” he said, flanked by Mexico’s top military commanders.

Michoacan, and especially its lowland Tierra Caliente, or Hot Land region, has been a smoldering battleground for years. The state is a major site of methamphetamine production, and drug gangs also squeeze local businesses and villagers with schemes to extort payments.

Repeated attempts to pacify Michoacan have floundered. The state was the first place Felipe Calderón deployed troops when he took office as president in December 2006. His successor, Peña Nieto, ordered a military surge there in May, as the ascendant local cartel, the Knights Templar, continued to terrorize towns and torch businesses and homes of anyone challenging its power.

Exasperated villagers in some towns have formed their own militias, or “self-defense groups,” to ward off attacks, adding a volatile element to the conflict. The Mexican government has struggled to demobilize them and to sort out which groups are actual vigilantes and which are really front groups for the gangsters.

Hipolito Mora, a militia leader in the town of La Ruana who has battled the Knights Templar, said the gang is “mad” because “the army is here, and more and more self-defense groups are rising up.”

“That’s why they’re attacking the federal police,” he said in a radio interview Thursday.

The militias have set up makeshift checkpoints along highways in the state and patrol their towns with shotguns, rifles and illegal automatic weapons of mysterious origin. In several parts of Michoacan, they have stirred the wrath of the cartels.

On Monday in the town of Los Reyes, gunmen opened fire on a crowd protesting the Knights Templar, killing five people. The attackers unleashed a fusillade of more than 100 rounds before fleeing.

In another Michoacan town Wednesday, a group of masked villagers wearing white “self-defense group” T-shirts stormed the offices of their municipal government and stole away with the police department’s automatic weapons, along with two patrol cars.

The mayhem in the state is becoming the same “stumbling block” for Peña Nieto that it was for Calderón, with criminal groups posing an “open challenge” to the government, said Mexico City-based security analyst Jorge Chabat.

“Presidents change, but the problems of violence and insecurity are still there,” Chabat said. “These are structural issues that are the result of government failure. And they will be very difficult to fix.”