Amnesty International has appealed for the immediate and unconditional release of all hostages in Iraq including Irish journalist Rory Carroll.
Amnesty condemned the use of hostages as bargaining tools by militants opposed to the US-led occupation of their country.
The organisation's appeal comes on the day angry Iraqi reporters held an impromptu memorial for the secretary of the Iraqi Journalists Union.
Mohammed Haroon (37) was shot dead by unknown gunmen making him the 56th journalist to be killed in Iraq since the invasion in 2003, according to the New York-based Committee to Protect Journalists (CPJ).
Another 22 media workers have been killed during the same time period. Nineteen journalists have died at the hands of Iraqi insurgents; at least eight others have been killed by fire from US forces, according to the CPJ.
Mr Haroon edited Baghdad's al-Hakeka( The Truth) which he set up in 2004. It was critical of the Baghdad government and the US presence in Iraq.
Reporters Sans Frontieres, another media rights group, has said the number of journalists killed Iraq war has surpassed the 20-year-long Vietnam wars - and is now the most lethal conflict for journalists since the second World War.
Four Reuters journalists have been killed in Iraq since 2003, at least three of them by US fire. Iraqi journalists also complain of frequent arrests by Iraqi and US forces, and Mr Carroll had recently written about the subject.
At least three Iraqi journalists working for Reuters are being held without charge by US troops, one of them for four months, with no clear prospect of release.
Mr Carroll was kidnapped yesterday in Sadr City while on assignment for British newspaper the Guardiancovering the trial of deposed leader Saddam Hussein.
"Rory Carroll's current work involves independent reporting on the trial of Saddam Hussein. Journalists like Rory are playing a critical role in reflecting the truth to the world, and his abduction is an affront to a free press. It's an outrage and unacceptable," Amnesty International's Irish Section secretary general, Colm O Cuanachain, said.