Gunmen on Friday killed a Mexican journalist who had received threats after reporting on corruption in the southern state of Chiapas, his newspaper said, in what was at least the ninth murder of a reporter in the country this year.

Mario Gomez, a reporter with El Heraldo de Chiapas, is the latest victim in a wave of violence against the press in Mexico, the second-deadliest country in the world for journalists after war-torn Syria, according to the watchdog group Reporters Without Borders.

"He had recently filed a complaint because he was receiving threats," a colleague at the paper told AFP on condition of anonymity.

Gomez, 35, had also been threatened in 2016 for publishing articles on corruption by two state officials, according to the media rights group Article 19.

El Heraldo said Gomez, a general news correspondent in the town of Yajalon, was leaving his house to go to work when two unidentified men arrived and "murdered him in cold blood" with a series of shots to the abdomen at point-blank range.

Gomez was taken to the hospital but died of his wounds, said the paper, where he had worked for the past eight years.

"We call for an exhaustive investigation to find those responsible for this crime," his colleagues wrote in an editorial published on the newspaper's website.

The state prosecutor's office said in a statement it would "follow all lines of investigation to shed light on this reprehensible crime and bring those responsible to justice."

Racked by violent crime linked to its powerful drug cartels, Mexico registered a record number of murders last year: 28,702.

That included at least 11 murdered journalists.

Asking questions about the multibillion-dollar narcotics trade, government corruption or the links between the two can be a deadly job in Mexico.

Including Gomez, at least nine journalists have been murdered so far this year in the country in possible retaliation for their work.

More than 100 have been murdered in Mexico since 2000.

The vast majority of the cases have gone unpunished -- as do more than 90 percent of violent crimes in Mexico.

It was not immediately clear whether Gomez was enrolled in the Mexican government's protection program for journalists and human rights activists, launched in 2012 in a bid to stop such crimes.

The program provides bodyguards, panic buttons and other protective measures to people at risk. But it suffers from under-funding and has failed to stop several high-profile murders.

It risks running out of funding in January, if the government does not bridge a budget gap.

Gomez's murder "saddens and burdens us, just as we're facing the lack of resources for the government's protection program for at-risk journalists," said Balbina Flores, Mexico representative for Reporters Without Borders.

"We demand a full investigation and a guarantee of security for his family."