The Institutional Revolutionary Party, or PRI, candidate for mayor of Villaflores, a city in the southern Mexican state of Chiapas, has been accused by an official of the rival National Action Party, or PAN, of murdering a member of that political party.

Ulises Grajales Niño murdered PAN member Edgar Hernandez Corzo, the 25-year-old nephew of congressional candidate Roger Decoss Corzo, early Monday, the PAN's leader in Chiapas, Carlos Palomeque, said.

Hernandez Corzo was murdered at the El Sinaloense ranch on the Villaflores-Chanona highway as he returned with three other people from painting PAN campaign slogans in the area, Palomeque said.

"After painting walls and distributing campaign literature for the blue-and-white (PAN) candidates, he was followed and caught by subjects in a vehicle in the area near that city," Palomeque said.

Authorities must investigate and find those responsible for killing Hernandez Corzo, the PAN state leader said.

Grajales Niño's candidacy has been cancelled and he should cooperate with investigators to clear up the incident, the PRI's state chairman in Chiapas, Roberto Albores Gleason, said in a statement.

"Our role as a political institution is without a doubt to not incriminate anyone, but we will not ignore acts of violence. As a result, we are asking the authorities to move quickly to clear up the legal status of Ulises Grajales," Albores said.

The Chiapas Attorney General's Office has opened an investigation to determine who was involved in the killing.

The PAN National Committee condemned Hernandez Corzo's killing and called on officials to investigate the incident "since an act of this nature cannot go unpunished, and we call for the punishment of those responsible to be expedited."

"National Action regrets this murder and expresses its most deeply felt condolences to the family of Hernandez Corzo," the PAN National Committee said.

A candidate for a seat in the Guerrero state legislature, meanwhile, was gunned down Monday at his house.

Margarito Genchi Casiano, a member of the leftist Party of the Democratic Revolution, or PRD, was killed around 7:00 a.m., the Guerrero Attorney General's Office said.

The politician was murdered by several gunmen who went to his house in Llano Largo, a community on Guerrero's Costa Chica.

Investigators have not determined the motive for the murder, which comes as the campaign for the July 1 general elections enters the home stretch.

Mexico's presidential campaign ends on June 27, four days before some 80 million voters head to the polls to cast ballots for a new president, 628 legislators and thousands of other officials. EFE