But another Reuters cameraman was released after being held for three days by US troops following an incident in which his soundman was shot dead, apparently by American soldiers.
Ali Omar Abrahem al-Mashhadani was arrested by US forces on 8 August after a search of his home in the city of Ramadi. The US military has refused Reuters' requests to disclose why he is being held. He has not been charged.
His brother, who was detained with him and then released, said they were arrested after US marines looked at the images on the journalist's cameras.
"The CRRB has determined that Mr Mashhadani remains a threat to the people of Iraq and they recommended continued internment," Lieutenant Colonel Guy Rudisill said, referring to a hearing of the Iraqi-US Combined Review and Release Board held at a secret location in Baghdad on Monday.
He said al-Mashhadani would be entitled to a review of his case within 180 days and would be held at Abu Ghraib.
Rudisill said he would not be allowed to see an attorney, his family or anyone else for the first 60 days of his detention, which began in Abu Ghraib last week.
Reuters Global Managing Editor David Schlesinger said: "I am shocked and appalled that such a decision could be taken without his having access to legal counsel of his choosing, his family or his employers.
"I call on the authorities to release him immediately or publicly air the case against him and give him the opportunity to defend himself."
Marines searched al-Mashhadani's home, along with others in the Ramadi neighbourhood, after shooting in the area.
Such shooting is common in the city, where Sunni Arab fighters are active. Reuters assigned al-Mashhadani to film such incidents.
Rudisill said he was aware of five journalists for major news media in detention, including al-Mashhadani and another freelance cameraman who has worked for Reuters, as well as a cameraman for the US television network CBS.
The New York-based Committee to Protect Journalists (CPJ) and the media watchdog group Reporters Without Borders both voiced alarm at al-Mashhadani's detention.
"This is simply unacceptable," CPJ Executive Director Ann Cooper said in a statement. "Through these detentions the US military gives every impression that it is not accountable. That's a bad example to give the citizens of an emerging democracy."
Reuters had also been pressing for the release of cameraman Haider Kadhem, who was detained in Baghdad on Sunday after an incident in which his soundman, Waleed Khaled, was killed as he drove the pair on a news assignment.
Iraqi police said US troops fired on the Reuters team, both Iraqis.
The US military said Kadhem, 24, was questioned about "inconsistencies" in his statements after the incident, before being released on Wednesday. He suffered superficial wounds from flying fragments.