On Wednesday, authorities announced having discovered Aide Nava's decapitated body the previous day in the state of Guerrero. According to local media, the criminal gang Los Rojos has threatened other politicians with the same fate suffered by the 42-year-old, who was running for mayor in the town of Ahuacuotzingo.

"It is a very lamentable case, and of heavy significance," Guerrero Attorney General Miguel Angel Godinez said on Wednesday. "For that, we have to manage it with a lot of care."

In 2014, narcotics criminals had murdered Nava's husband, the former mayor of Ahuacuotzingo. Meanwhile, their son, kidnapped last year, remains missing.

"We are sorry for the murder of Aide Nava and demand an investigation," Celestino Cesareo Guzman, the head of Nava's Democratic Revolutionary Party (PRD) in Guerrero state, said on Wednesday. "She was taken from a political meeting in the community, and lamentably they ended her life," Guzman said.

Mexicans will head to the polls on June 7 to vote for federal legislators and state and local officials.

'History of violence'

Last year, the state of Guerrero became the focus of international media attention after 43 trainee teachers disappeared in a case thatmay have involved German weapons. Los Rojos, the gang implicated in Nava's murder, rival Guerreros Unidos, the cartel believed to have killed the students in September.

According to the government, corrupt local police had abducted the students in league with Guerreros Unidos. According to the United Nations, such disappearances occur frequently in Mexico.

The attorney general's office accused Iguala Mayor Jose Luis Abarca - like Nava, a PRD official - and his wife of masterminding that crime. The case put the PRD in crisis mode.

The party's former governor in Guerrero, Angel Aguirre Rivero, resigned amid street protests last year. Salvador Ortega Martinez, the interim governor elected by the state legislature to serve through the end of March, is also a PRD member.

More than 100,000 people have died in violence linked to drug cartels in Mexico during the past eight years. President Enrique Pena Nieto, who pledged to restore order to Mexico when he took office in December 2012, had to contend with a string of major street protests over the disappearance of the students on the night of September 26, 2014, in the city of Iguala.

Despite the deployment of thousands of federal police officers and soldiers, Guerrero remains Mexico's most violent state. Last week, authorities did manage to arrest the Zetas cartel boss in Nuevo Leon. In late February, they captured the chief of the Knights Templar in Michoacan.

mkg/gsw (EFE, Reuters, AFP, dpa)