Antonio de la Cruz, a journalist for local newspaper Expreso, was shot and killed in his home in the Tamaulipas state capital Ciudad Victoria, the paper he worked for said.
Tamaulipas is a Gulf coast state, just south of Texas, where violent drug cartels fight over lucrative smuggling routes. Local journalists who focus on crime and corruption are especially vulnerable.
De la Cruz's death follows at least eight other media workers who have been murdered in Mexico this year as a result of their journalism, according to human rights organization Article 19.
Early clues "suggest that his murder may be linked to his political criticism" as a journalist, Leopoldo Maldonado, regional director of Article 19 in Mexico and Central America, told Reuters.
The journalist's daughter was injured in the attack. Tamaulipas Governor Francisco Garcia Cabeza de Vaca said on Wednesday afternoon she was in critical condition.
"We're not going to stop until we find those responsible, and we're going to punish them with the full weight of the law," the governor said.
The paper's parent company Expreso-La Razon demanded justice.
The Tamaulipas attorney general's office said in a statement it had opened an investigation, and police are collecting evidence and hunting for the attackers. It will provide an update in several hours, the governor said.
Violence against the press has skyrocketed during Mexican President Andres Manuel Lopez Obrador's administration, according to a report published by Article 19.
Several organizations such as Mexico's federal journalists' protection program, Article 19 and the Committee to Protect Journalists told Reuters they had no records of the journalist having received threats.
(Reporting by Valentine Hilaire, Lizbeth Diaz and Kylie Madry; Editing by Bill Berkrot, David Alire Garcia, Sandra Maler and David Gregorio)
By Lizbeth Diaz and Kylie Madry
