Villahermosa, Mexico: The nephew of one of Mexico's most-wanted drug gang leaders was captured together with a police chief accused of protecting a notorious cartel in a key port city, authorities say.

Federal police detained Roberto Rivero Arana, who identified himself as the nephew of reputed Zetas gang leader Heriberto Lazcano, in the Gulf coast state of Tabasco after three months of intelligence work, the Attorney General's Office said in a statement issued late on Tuesday.

He was detained along with Daniel Perez, the acting police chief of Ciudad del Carmen, an oil hub in neighbouring Campeche state. The statement alleged Perez received 200,000 pesos (Dh58,751) a month for protecting the Zetas.

The arrests come as the Zetas are under pressure from a bloody turf war with their former ally, the Gulf cartel. Authorities blame that fight for contributing to a surge of violence in Mexico's northeastern border states north of Tabasco and Campeche.

Perez was acting chief pending a permanent appointment, Ciudad del Carmen Mayor Aracely Escalante said on Wednesday.

Invested trust

"He's an agent who had been with the police force long before we took over the town government," Escalante said. "We had given him our trust."

The two men were found with 10 assault rifles, a grenade, ammunition, drugs, police uniforms and worker suits with the logo of Mexico's state oil company, Pemex, the Attorney General's Office said.

Last week, Tabasco Gov. Andres Granier warned that the arrests of several suspected Zetas over the past several months could stoke turf battles in his region. He asked the federal government to send troops.