The Islamic State group beheaded four journalists in Iraq, according to German news agency DPA. Residents of Iraq’s northern city of Mosul said militants delivered four bodies to medical officials Tuesday. Their names and nationalities have not yet been released.

The four victims are thought to be among the 12 journalists, all of them Iraqi, that the group formerly known as ISIS abducted last week. International Business Times was not able to independently confirm the reports.

Since ISIS entered Iraq this summer and declared a caliphate, the militants have been on a crusade against media activists and journalists. Mosul security officials said that the militants captured at least 19 journalists in Mosul in the past three weeks.

“For the second time, IS insurgents have started to kidnap journalists in Mosul. This time they have kidnapped 12 journalists and taken them to unknown locations,” a security official told BasNews.

Three reporters were confirmed missing in Mosul two weeks ago, and human rights officials said they were captured by ISIS. The Guardian identified the captives as broadcast journalist Talal Qais and cameramen Walid Akidi and Ashraf Abadi.

Last month, it was reported that ISIS executed Iraqi Kurdish journalist Muhannad Akidi just outside of Mosul after he had been held captive by the militants for two months. Reporters Without Borders has not been able to confirm the reports.

ISIS released four videos purporting to show the beheading of U.S. journalists James Foley and Steven Sotloff and British aid workers Alan Henning and David Haines.  

"Killing of journalists is the ultimate form of censorship. ... If there is no immediate and serious response by the government, journalists feel threatened and self-censor," Sherif Mansour, the Committee To Protect Journalists Middle East and North Africa Program Coordinator, wrote in a recent report on the state of Iraqi journalists in Kurdistan. "For every journalist killed or imprisoned, dozens more are silenced."