"The failure of the US military to provide an honest and open accounting of what occurred keeps alive questions about whether US forces are taking the necessary steps to avoid endangering journalists," said CPJ Executive Director Ann Cooper.
"These questions are urgent because hundreds of journalists continue to work in Iraq, and their reporting is vital for the world's understanding of events in this post-war period," Cooper said.
The New York-based CPJ said it had refiled three new freedom of information requests with the Defence Department, seeking clarification on the US shelling of the Palestine Hotel in Baghdad and an air strike on the Baghdad bureau of Qatar-based satellite broadcaster Al-Jazeera.
Both incidents occurred on April 8 and resulted in the deaths of three journalists.
The CPJ is also seeking answers over the shooting by US troops of Reuters cameraman Mazen Dana on August 17.
Previous requests for information had been rewarded by only summary explanations or, in some cases, no explanation at all, Cooper said.
The CPJ called on the Pentagon to order US commanders to review their operational guidelines and rules of engagement, so as to address the need to pay special attention to protecting journalists.