BOCA DEL RIO, Mexico - Grieving, frightened journalists remembered three slain colleagues on Friday as young and energetic members of a press corps working under terrifying conditions in a state torn by a war between Mexico's two most powerful drug cartels.

Traffic dwindled from the streets and shopping areas emptied hours after the discovery Thursday afternoon of Guillermo Luna Varela, Gabriel Huge, Esteban Rodriguez and Irasema Becerra, who had been slain, dismembered and stuffed into black plastic bags dumped into a waste canal.

It was a sense of dread familiar to Veracruz, where a cartel battle for control of one of Mexico's largest ports has spawned horrors such as the slaughter of 35 people dumped on a main highway in rush-hour traffic in September.

The state is a common route for drugs and migrants coming from the south on the way up to the United States. Much of the area around its main port city on the Gulf of Mexico was controlled until last year by the Zetas, a brutal paramilitary-style cartel founded by defectors from the Mexican army special forces and known for its gruesome butchery of opponents.

Late Friday, state prosecutors said in a statement police had found three oil drums containing human remains along a highway connecting the port city of Veracruz with Xalapa after receiving an anonymous tip. They offered no other details.

Last year, the Zetas' territory in Veracruz came under assault from the New Generation, a cartel based in the western state of Jalisco and allied with the powerful Sinaloa cartel, which is led by kingpin Joaquin "El Chapo" Guzman.

Drug cartels battling for control of smuggling routes often use threats, bribes or both to demand the support of local officials, prison directors and other influential people in the cities they are fighting over. Journalists have not been spared.

"We're living in madness," a Veracruz newspaper editor told The Associated Press, speaking on condition of anonymity for his safety.

He said Zetas had wanted him to publish news about the killings of Sinaloa soldiers, and the New Generation had pressured him to suppress such reports.

"The Zetas talk to you and tell you not to publish something, and the New Generation talks to you and say, 'If this isn't published, I'll mess you up.' So what are we supposed to do?"

He said criminal gangs even had de facto press representatives, who emailed complete stories for media to publish.

A local television reporter said his cameramen had once been warned off covering a story by the cartels - by a fellow journalist who worked for a gang. He also spoke on condition of anonymity out of fear.

At least seven current and former reporters and photographers have been slain in Veracruz over the last 18 months, forcing their surviving colleagues to work under precautions reminiscent of those in a war zone. Journalists let colleagues and family know by phone when they are leaving for work and coming home. They call ahead before covering a story to see if the area is safe. Once they go, they move in groups of four or five and scan areas from the vehicle before getting out, remaining in constant contact with their newsroom. Few talk anymore with strangers, a new reticence in an area once known for its tropical warmth and welcoming attitude to tourists and other visitors.

Press freedom groups said all three slain photographers found Thursday had temporarily fled the state after receiving threats last year.

Huge, a new father who was in his 30s, and Luna, his 22-year-old nephew, were "part of a new generation of young photographers who permeate the media in Veracruz," wrote Sandra Segura, a columnist for the newspaper Notiver, where both men had worked. Both had covered the police beat.

"They were all spouses, children, siblings, parents, like Gabriel, the father of a 2-year-old girl. All of them had a future snatched away in an instant," she wrote.

Friends and relatives of Huge and Luna filled the single-story cinderblock house where Luna had lived with his family. The bodies of the two men lay in open coffins but covered in white sheets. Luna's favourite baseball cap rested on his sheet.

Luna's mother, Mercedes Varela, said she had begged him to leave journalism, but he had refused, saying he had nothing to fear. She described her son as a ferociously dedicated journalist who listened constantly to all-news radio.

The sound filled their small house at all hours, Varela said.

"I'm going to miss that," she added.

The victims were discovered less than a week after Regina Martinez, a correspondent for the national magazine Proceso, was found beaten and strangled in her home in the state capital of Xalapa.

Martinez was one of the few reporters in Veracruz who continued to work on drug cartel-related stories. Her last story for the magazine was about the arrest of nine police officers accused of links to drug traffickers, but she did not work on any of the longer-term stories that have gained Proceso a reputation for deep investigations that anger the powerful in Mexico, according to a high-ranking editor at the paper, who spoke on condition of anonymity because he was not authorized to release the information. The editor said Martinez scrupulously checked with her editors before beginning reporting on any story, and she had not been working on anything for Proceso at the time of her death.

A Mexican military official with direct knowledge of the situation in Veracruz said that the New Generation had been systematically killing Zeta members in Veracruz and since the end of 2011 had taken control of the city of Veracruz and its valuable port. Zetas continue to control the city of Xalapa and many small municipalities around the city of Veracruz, the official said, speaking on condition of anonymity because he was not authorized to release the information.

Local law enforcement in the state was considered so corrupt and infiltrated by the gangs that Mexico's federal government fired 800 officers and 300 administrative personnel in the city of Veracruz-Boca del Rio in December and sent in about 800 marines to patrol.

Prosecutions for murder, including those of journalists, are rare in Mexico.

In June, Miguel Angel Lopez Velasco, a columnist and editorial director for Notiver, was shot to death in Veracruz along with his wife and one of his children.

Authorities that month also found the body of journalist Noel Lopez buried in a clandestine grave in the town of Chinameca. Lopez, who disappeared three months earlier, had worked for the weeklies Horizonte and Noticias de Acayucan and for the daily newspaper La Verdad.

The following month, Yolanda Ordaz de la Cruz, a police reporter for Notiver, was found with her throat cut in the state.

Lopez was found after a suspect in another case confessed to killing him, but the other two murders have not been resolved.

Around the time of the killings, Luna received a phone threat that told him not to publish a recent piece of work, and prompted him to flee, said Martin Lara, director of veracruznews.

"The voice on the phone told Luna that "he knew where he lived, and he didn't want that (story) to come out,'" Lara said, without providing any details.

Rodriguez, the third victim, was a crime photographer for the local newspaper AZ until last summer, when he too quit and fled the state. He later came back, but took up work as a welder.