In Veracruz, the body of reporter Victor Baez was found early Thursday in the state capital of Xalapa after gunmen intercepted him as he left his newsroom, the Los Angeles Times reported.
He became the eighth journalist to be killed in Veracruz in the past year and one of dozens killed or kidnapped in Mexico since President Felipe Calderon began a military-led offensive against drug cartels.
The Times said Baez, like many of the reporters killed, had covered the crime beat.
In Veracruz, journalists say they believe they're being targeted before the July 1 election because the Institutional Revolutionary Party is worried about election losses in the region and doesn't want coverage of campaign improprieties.
The party says its campaign is clean.
Some reporters wept at a news conference during which Veracruz government spokeswoman Gina Dominguez said, "This crime is intended to intimidate society and force the government to step back in its efforts to fight crime."
In the northern border state of Coahuila, journalist Stephania Cardoso was abducted with her 2-year-old son last week and both remaining missing. Her family said her home was ransacked and her work camera smashed but nothing was stolen.
Institutional Revolutionary Party candidate Enrique Pena Nieto, who appears likely to win the presidency, has disavowed violence.
The Times said an activist with Calderon's conservative National Action Party was killed in Chiapas state, allegedly by an Institutional Revolutionary Party operative, who has been arrested.
Margarito Genchi, a candidate for the state legislature in Guerrero from the leftist Democratic Revolution Party, was killed Monday.
The next president will face corruption that sometimes involves drug traffickers, the Times said.
Police are suspected of acting on orders from drug gangs in the death of three men seen in a video released this week being marched by officers from a hotel at night.