President Andrés Manuel López Obrador said Thursday that the killings of journalists in Mexico will not go unpunished and he told the son of a slain reporter that he has arranged for him to meet with federal Attorney General Alejandro Gertz Manero.

Carlos Dominguez asked for López Obrador's help at the president's daily press briefing. His father, a longtime journalist with the same name, was stabbed to death in broad daylight in downtown Nuevo Laredo in January 2018.

Dominguez says the alleged mastermind behind the killing is a former mayor of the northern border city, Carlos Canturosas, who the elder Dominguez had been investigating for alleged malfeasance. Canturosas has denied any involvement.

"I'm desperate, I'm afraid," the younger Dominguez said. "Help me find justice for my dad."

Six men were arrested last year in the case, including Canturosas' uncle.

López Obrador said his administration would ask the federal Attorney General's Office to take over the case from state prosecutors. The agency's prosecutor for crimes against freedom of expression, which includes the killing of journalists, had already been involved in the case, but the Tamaulipas state prosecutor's office had the lead.

"We have to do away with impunity," López Obrador said.

The younger Dominguez also asked the president to intervene because Canturosas' sister was running for a state legislative position as a candidate for López Obrador's Morena party. López Obrador demurred on that point, saying he would not get involved in local politics.