Resarch by the Bureau of Investigative Journalism has reported just 4 percent of US drone strikes in Pakistan have killed people identified as members of al-Qaeda.

Research by the London-based bureau found that only 111 out of the total 2,379 drone victims killed in Pakistan since 2004 was "a senior commander of any armed group". Just 84 victims were identified as al-Qaeda militants.

Following the 400th drone strike on 11 October, the report provides a damning assessment of the CIA drone program in Pakistan.

"More than a third of them were not designated a rank, and almost 30 percent are not even linked to a specific group. Only 84 are identified as members of al-Qaeda – less than 4 percent of the total number of people killed," the report said.

The investigative bureau's Naming The Dead project has been monitoring and collating research on the identities and backgrounds of US drone victims in Pakistan since June 2004.

The project is based on years of research from a wide range of sources in and outside Pakistan. Some of the obtained documents were leaked by an anonymous source in the Pakistani government.

The leaked files reveal how the CIA has free rein to carry out drone strikes on any target without having to inform the Pakistani government.

The US government only has to determine that a terrorist is an imminent threat if it wants to use a drone strike. It "does not require the United States to have clear evidence that a specific attack on US persons and interests will take place in the immediate future".

The CIA has previously been criticized for apparently not knowing the affiliation of everyone it kills in drone strikes. Leaked files revealed hundreds of drone victims were labelled as "unknown".

The controversial drone program has also operated in terror hot spots such as Yemen, Iraq and Afghanistan.