Family members said they did not want the name of their son, who was 30, mentioned in this report.
He was killed on Wednesday along with two of his brothers while they were in a car near the Diyala bridge in the capital, an area known to be rife with Shi'ite and Sunni militants.
It appears the killing was one of the dozens of executions carried out every day in Baghdad by sectarian death squads that roam the city despite the presence of some 100,000 U.S. and Iraqi security forces in the city.
Reuters staff in Baghdad became concerned about their colleague when he did not show for work on Saturday. He came to the office four days a week, always taking Thursday and Friday off, and had worked for Reuters since March.
He was the third Iraqi working for the international news and information company to be killed this week.
Reuters photographer Namir Noor-Eldeen, 22, and driver Saeed Chmagh, 40, were killed in Baghdad on Thursday in what witnesses said was a U.S. helicopter attack and which police described as "random American bombardment."
The military described it as a firefight with insurgents.
In addition to that, gunmen shot dead an Iraqi reporter working for the New York Times while he was on his way to work in Baghdad on Friday. Khalid Hassan was 23.
Our colleague had been careful to ensure no one knew he was working for the foreign media and preferred that his name did not appear on stories.
Always cheerful and polite, he was a very precise translator who also worked in a small business enterprise.
He was married with two daughters, aged 3 years and 8 months. He was the seventh person working for Reuters to be killed in Iraq since the U.S.-led invasion in 2003.
Two other Iraqi journalists working for Reuters have been killed by U.S. soldiers. Two foreigners, a Palestinian and a Ukrainian, have also been killed by American troops. The U.S. military has said its soldiers acted lawfully in those cases.
Iraq is the world's most dangerous country to report, especially for Iraqis who are often attacked by insurgents intent on silencing their voices, media watch groups say.
The Committee to Protect Journalists in New York has estimated that at least 149 reporters and media assistants have been killed since 2003. The vast majority have been Iraqis.