(CNN) Three journalists in Mexico were killed this week, bringing to at least 10 the number of reporters slain in the country this year.

In the southern state of Guerrero, Edgar Alberto Nava and Rogelio Barragan were killed days apart, and authorities have not said if the two killings are connected or linked to the victims' work as journalists. The state of Guerrero, many territories of which are controlled by drug trafficking organizations, has one of the country's highest homicide rates, the research initiative Justice in Mexico says.

Nava was killed Friday in Zihuatanejo de Azueta. Nava was "was shot with a 9mm caliber firearm," the state attorney general's office said. An investigation is ongoing, the office said.

Nava worked for the news outlet La Verdad de Zihuatanejo. He also worked as a municipal employee, the Knight Center for Journalism in the Americas said.

Jorge Sánchez Allec, the mayor of Zihuatanejo de Azueta, said he was "deeply sorry for the attack against my friend and colleague Edgar Nava."

On July 30, Barragan was found dead inside a car with his hands tied and signs of torture, according Mexico's government run news site Notimex. Barragan, who worked for the digital news outlet Guerrero Al Instante, was found dead in Zacatepec, a town in the state of Morelos that is not far from Guerrero.

In the southern state of Veracruz, Jorge Ruíz Vázquez was killed Friday, Gov. Cuitláhuac García said.

García vowed a "coordinated operation to capture the culprits."

The Secretary of Public Security of the State of Veracruz, Hugo Gutiérrez Maldonado, tweeted that he condemns "strongly the murder of the journalist" who worked as a correspondent for the graphic newspaper, Xalapa.

Mexico is the most dangerous country for journalists in the Western Hemisphere, the Committee to Project Journalists (CPJ) says.

CPJ's Mexico Representative Jan-Albert Hootsen called for "an immediate and credible investigation" into both deaths.

"These two brutal killings within days of each other are the tragic consequence of Mexico's failure to seriously address impunity in attacks on the press," Hootsen said in a statement.

Mexico's National Human Rights Commission also condemned both killings and urged authorities to investigate.

Reporters Without Borders, known internationally as Reporters Sans Frontières, or RSF, said earlier this week eight Mexican journalists have been killed in 2019 but the group has not yet reacted to Friday's killings.