MEXICO CITY (AP) — A band of gunmen killed an environmental activist who had received death threats for standing up to drug gangs and had a police guard when she was ambushed in southern Mexico, authorities said Thursday.

Juventina Villa Mojica, whose husband and two children were killed last year, died in a hail of bullets along with her 10-year-old son Wednesday in a mountainous area of the state, Guerrero state prosecutors said in a statement.

Her 7-year-old daughter survived unhurt during the attack by at least 30 assailants, said Manuel Olivares, a human rights activist who knew Villa.

Villa and her late husband, Ruben Santana Alonso, had led for more than 20 years a group of farmers in the village of La Laguna, which is part of the municipality of Coyuca de Catalan. The area is ridden by drug traffickers who have been seeking to expand their marijuana and opium-poppy fields.

"It's a virgin area with rich forest areas, and the main interest of drug traffickers is cutting down the trees so that once it is deforested they can expand their drug fields," Olivares said.

Drug gangs began targeting Villa, her husband and their extended family after they refused to allow drug traffickers to cut down trees near their village, he said.

Villa and her children had ridden in an all-terrain vehicle near the top of a mountain where she could get a cellphone signal since there are no telephones in the village. They were ambushed despite the presence of 10 state police officers who were protecting them, state prosecutors said in a statement.

Five of the officers were in a patrol car ahead of Villa and her children and the other five where on foot behind them, the statement said. Villa got ahead of the officers on foot and that's when the assailants fired their weapons, it said.

Prosecutors didn't say whether the officers fired at the attackers. Calls to prosecutors went unanswered Thursday.

Local media said Villa had filed a complaint with authorities in early November after two of her nephews were killed and several farmers received death threats.

More than 20 members of her family and her husband's family have been killed since last year, Olivares said. State authorities assigned 31 police officers to protect La Laguna, but Villa and other villagers had asked to be relocated, he said.

Some families were supposed to be temporarily relocated Wednesday to the community of Puerto de la Ollas but authorities didn't show up, Olivares said.

"We insisted with the government that it was urgent to get people out of that region, but we encountered little willingness to help," he said.

The Guerrero state-based Tlachinollan Center for Human Right said in a statement that the slaying of Villa and her son could have been avoided if state authorities "had heard the cries of the victims of this violence that is blinding the life of poor and helpless families."

"The failure of authorities to act and the impunity that reigns in the region have resulted in this unstoppable violence where organized crime groups have imposed their law through terror," the center said.

The state government said in a statement late Thursday that the area has suffered from longstanding problems that pre-date the current administration, which has been in office since early 2011.

"The mountain region has been marked by various conflicts related to drug plantations, hit squads, killings related to family feuds, illegal logging and other conflicts related to organized crime and drug trafficking," it said, adding that "the current conflicts in the region date back at least 15 years."

The government noted 31 police officers had been assigned to protect the relocated families around the clock and said Villa's death "resulted from the fact she left the protected area."