Edgar Daniel Esqueda, 23, who worked with Metropoli San Luis and Vox Populi SLP in the state of San Luis Potosi, was found in the state capital with at least three bullet wounds in the back of his neck, authorities said.
The news outlets where Esqueda worked reported had reported his abduction from his home by gunmen on Thursday morning.
San Luis Potosi's governor, Manuel Carreras, told a press conference an investigation was underway. He did not say whether Esqueda's murder was linked to his work as a journalist.
With Esqueda's killing, 2017 could become the bloodiest year yet for reporters in Mexico, according to press freedom and journalists' advocacy group Articulo 19.
The photo journalist was the 11th reporter killed so far this year, the group said. That matched the total in 2016, which was the highest number on record in a country torn by runaway levels of criminal and drug-related bloodletting.
Over the past 17 years, 111 journalists have been killed in Mexico, 38 of them under the current government of President Enrique Pena Nieto.
Reporters Without Borders and the Committee for the Protection of Journalists (CPJ) both rank Mexico among the deadliest countries in the world for reporters.
Activists have repeatedly criticized Mexican prosecutors for failing to fully investigate many journalists' murders, allowing the killers to operate with impunity.
Mexico's human rights commission has asked state authorities to provide protection for Esqueda's family members, who were at home with the photographer when he was taken by force, according to Articulo 19.
Witnesses who spoke with the group said Esqueda asked his kidnappers for their identity when they broke into the home where he was asleep with his wife, and they responded that they were police officers.
The state police force said via Twitter that "there has not been any police action against a reporter in the capital."
"Criminals, sometimes connected with state actors, know that they can get away with killing journalists in Mexico because of chronic impunity for these crimes. Until that changes, the violence will continue," Alexandra Ellerbeck, the CPJ's programme coordinator for North America, said in a statement.
Esqueda had reported threats months ago to a government-run human rights group in San Luis Potosi, one of his colleagues told Reuters.
(Reporting by Daina Beth Solomon and Christine Murray; Editing by Tom Brown)
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