Spanish cameraman Jose Couso, of Telecinco, and Taras Portsyuk, a Ukrainian cameraman for Reuters, were killed April 8 when U.S. forces struck the Palestine Hotel.
The Pentagon has said the shelling was in response to hostile fire from the hotel, where Couso, Portsyuk and about 100 other journalists were staying.
But the report, released Tuesday by the Committee to Protect Journalists, said journalists monitoring the fighting from their balconies disputed that U.S. troops had been fired upon from the hotel.
"There is simply no evidence to support the official U.S. position that U.S. forces were returning hostile fire from the Palestine Hotel," the report said.
Instead, the report suggests that U.S. forces fired while searching for a suspected Iraqi "spotter," or forward observer.
Pentagon officials knew the hotel was occupied by foreign journalists and were determined to avoid it, but the tank commander who fired the round wasn't aware of their concern, the report found.
The report said that the attack, "while not deliberate, was avoidable," and called on the Pentagon to provide a "full, public accounting" of the incident.
In a letter to Spanish Foreign Minister Ana Palacio in April, Secretary of State Colin Powell said the U.S. review of the incident "indicates that the use of force was justified and the amount of force was proportionate to the threat against United States forces."