Iraqi journalist Hadi al-Mehdi, who has been a prominent critic of the government on his radio programme, was shot dead in Baghdad on Thursday, a security official and a medic said.
"Hadi al-Mehdi was shot dead in an apartment on Abu Nawas street at about 6:30 pm (1530 GMT)," an interior ministry official told AFP, adding that a silencer was used in the shooting.
A medical source at Ibn al-Nafis hospital in central Baghdad confirmed that Mehdi had been killed.
"We received the body of Hadi al-Mehdi, who died from a single gunshot to the head," the source told AFP.
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Media watchdog Reporters Without Borders (RSF) released a statement saying it "strongly condemns the assassination of Hadi al-Mehdi."
RSF noted that his murder came ahead of nationwide demonstrations planned for Friday, which Mehdi was known to support, and said that "the assassination was undoubtedly politically motivated."
Mehdi was well-known for his sharp critiques of government ineptitude and corruption on his show on Demozee radio, and was also a playwright.
He wrote commentaries for several websites including www.kitabat.com, which posted a tribute to him on Thursday, describing him as "the innovative artist, one of the most prominent leaders of the uprising of the people, the martyr Hadi al-Mehdi."
Mehdi was one of four Iraqi journalists detained by security forces following a protest in Baghdad in February.
He described the conditions of his detention as "brutal and inhuman", saying soldiers bundled him into the boot of a Humvee, tore off his shirt to blindfold him, subjected him to electrical shock treatment and repeatedly insulted him during interrogations.