Four of the last reporters and photographers willing to cover crime stories have been slain in less than a week in violence-torn Veracruz state, where two Mexican drug cartels are warring over control of smuggling routes and targeting sources of independent information. The brutal campaign is bleeding the media and threatening to turn Veracruz into the latest state in Mexico where fear snuffs out reporting on the drug war. Three photojournalists who worked the perilous crime beat in the port city of Veracruz were found dismembered and dumped in plastic bags in a canal Thursday, less than a week after a reporter for an investigative newsmagazine was beaten and strangled in her home in the state capital of Xalapa. Press freedom groups said all three photographers had temporarily fled the state after receiving threats last year. The organizations called for immediate government action to halt a wave of attacks that has killed at least seven current and former reporters and photographers in Veracruz over the last 18 months. Like most of those, the men found Thursday were among the few journalists left working on crime-related stories in the state. Threats and killings have spawned an atmosphere of terror and self-censorship, and most local media are too intimidated to report on drug-related violence. Social media and blogs are often the only outlets reporting on serious crime. Veracruz isn't the only battleground for Mexican media. In at least three northeastern states, journalists are under siege from assailants throwing grenades inside newsrooms and gunmen firing into newspaper and TV station buildings. In the state of Tamaulipas, on the border with Texas, local media stopped covering drug trafficking violence, mentioning drug cartels or reporting on organized crime shortly after two gangs began fighting for control of Nuevo Laredo in 2004. As part of that war, reporters were targeted to keep them silent or because they had links to gangs. Mexico has become one of the world's most dangerous countries for journalists in recent years, amid a government offensive against drug cartels and fighting among gangs that have brought tens of thousands of deaths, kidnappings and extortion cases. Prosecutions in journalist killings are almost nonxistent, although that is widely true of all homicides and other serious crimes in Mexico. The latest killings came in Boca del Rio, a town near the port city of Veracruz where police found the bodies. The victims bore signs of torture and had been dismembered, the state prosecutors' office said. One victim was identified as Guillermo Luna Varela, a crime-news photographer for the website http://www.veracruznews.com.mx who was last seen by local reporters covering a car accident Wednesday afternoon. According to a fellow journalist, who insisted on speaking anonymously out of fear, Luna was in his 20s and had begun his career working for the local newspaper Notiver. The journalist said Luna was the nephew of another of the men found dead, Gabriel Huge. Huge was in his early 30s and worked as a photojournalist for Notiver until last summer, when he fled the state soon after two of the paper's reporters were slain in still-unsolved killings. He had returned to the state to work as a reporter, but it was not immediately clear what kind of stories he was covering recently. State officials said the third victim was Esteban Rodriguez, who was a 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. The London-based press freedom group Article 19 said he, like the other two, had been a crime photographer. The fourth victim was Luna's girlfriend, Irasema Becerra, state prosecutors said. Article 19 said in a report last year that Luna, Varela and Rodriguez were among 13 Veracruz journalists who had fled their homes because of crime-related threats and official unwillingness to protect them or investigate the danger. The Committee to Protect Journalists said in 2008 that Huge had been detained and beaten by federal police as he tried to cover a fatal auto accident involving officers. Last 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. The cartel war in Veracruz reached a bloody peak in September when 35 bodies were dumped on a main highway in rush-hour traffic. Local law enforcement in the state was considered so corrupt and infiltrated by the Zetas and other 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. Mike O'Connor, the Committee to Protect Journalists' representative for Mexico, said journalists in Veracruz were exercising an unusual degree of self-censorship even before Ordaz and Lopez were killed. He said media avoided much coverage of crime and corruption. "Important news was not covered because it might upset the Zetas. Then these guys were killed and self-censorship cracked down even more," O'Connor said. "Almost all of the police beat reporters left town after those killings." Regina Martinez, a correspondent for the national magazine Proceso, continued to cover crime-related stories along with a handful of other journalists, however. On Saturday, authorities went to her home in Xalapa, the state capital, after a neighbor reported it to be suspiciously quiet. They found the reporter dead in her bathroom with signs she had been beaten and strangled. "Self-censorship was extraordinarily strong but whoever killed these journalists wanted more," O'Connor said. "It still wasn't enough to satisfy whoever killed these journalists." Mexico's human rights commission says 74 media workers were slain from 2000 to 2011. The Committee to Protect Journalists says 51 were killed in that time. It noted in a statement on the Mexico killings that Thursday was World Press Freedom Day.