A Mexican journalist was found beaten to death Tuesday in the northern state of Tamaulipas, on the US border, prosecutors said, at least the fifth reporter murdered in the country this year.
Hector Gonzalez Antonio, a correspondent for national daily Excelsior and local radio and TV stations, was found bludgeoned to death on a road in the state capital, Ciudad Victoria, the state prosecutor's office said in a statement.
"An investigation has been opened to identify and locate those responsible for this homicide," it said.
Pictures from the crime scene showed the journalist's bloodied body, shirtless and missing a shoe, abandoned on a narrow dirt road on the outskirts of Ciudad Victoria.
Gonzalez, 40, had been kidnapped in a carjacking on Monday, said watchdog group Reporters Without Borders.
A married father of two, he covered politics and general news, including stories on the wave of violence that has engulfed Mexico in recent years -- which has hit particularly hard in Tamaulipas, the scene of bloody turf wars between rival drug cartels.
Tamaulipas is "a black hole as far as the freedom of the press, so it's very likely he was killed because of his work as a journalist," said Balbina Flores, head of Reporters Without Borders in Mexico.
Flores called for a full investigation and government protection for Gonzalez's family.
Racked by violent crime linked to the multibillion-dollar narcotics trade, Mexico posted a record number of homicides last year: 25,339.
That included at least 11 murdered journalists, making the country the deadliest in the world for the profession after Syria, according to Reporters Without Borders.
Asking questions about powerful drug cartels or government corruption can be a deadly job in Mexico.
Including Gonzalez, at least five journalists have been murdered so far this year in the country in possible retaliation for their work, and another is missing, according to the rights group.
More than 100 have been murdered in the country since 2000.
The vast majority of the cases have gone unpunished -- as do more than 90 percent of violent crimes in Mexico.
"When journalists are murdered or threatened for doing their jobs, freedom of expression is threatened," said Giancarlo Summa, director of the United Nations Information Center in Mexico.
"We demand the authorities investigate what happened (to Gonzalez) immediately and arrest those responsible. The impunity must end."
A colleague and friend of Gonzalez, who asked not to be named out of fear for his safety, said the late journalist's death did not appear to fit the profile of a typical drug cartel execution.
"It's strange that he was beaten to death and not shot," he said.
He said Gonzalez had not mentioned receiving threats, but was "very careful about what he wrote and said."
"It's dangerous to publish or comment on what happens here" in Tamaulipas, Gonzalez's friend told AFP.