The Islamic State of Iraq and the Levant (ISIL) has publicly executed a news cameraman and three civilians in northern Iraq, according to the journalist's relatives.

ISIL shot Raad al-Azzawi, 37, his brother and two other civilians on Friday in the village of Samra, east of Tikrit, in the country's Salaheddin governorate, the relatives said.

"They came to his home and took him and his brother," one relative said, speaking on condition of anonymity. "He did nothing wrong; his only crime was to be a cameraman. He was just doing his job."

Al Jazeera cannot independently verify the reports of the public executions.

The media watchdog Reporters Without Borders (RSF) said Azzawi, a father of three, was detained by ISIL members on September 7.

In a statement issued last month, RSF said that ISIL had threatened to execute Azzawi on the grounds that he had refused to work for the group.

Azzawi had worked for local news channel Salaheddin, which has been attacked by the group before.

In December, two suicide bombers stormed the channel's headquarters killing five journalists, including the channel's chief news editor, after accusing Salaheddin of "distorting the image of Iraq's Sunni community."

Death threat

Two American journalists and two British aid workers have been beheaded by ISIL in what the group says are retaliatory killings for the US-led air campaign against its fighters in Iraq and Syria.

Family and friends of Abdul-Rahman Kassig, a US humanitarian worker who ISIL are holding and threatening to kill next, held a prayer service on Friday, during which they highlighted his willingness to help others in the face of danger.

Kassig, a 26-year-old from the US state of Indiana formerly known as Peter Kassig, was threatened at the end of a video ISIL released last week that showed the beheading of British aid worker Alan Henning.