North Vietnamese made hoax calls to get the US military to bomb its own units during the Vietnam War, according to declassified information that also confirmed US officials faked an incident to escalate the war.

The report was released by the National Security Agency, responsible for much of the United States' codebreaking and eavesdropping work, in response to a "mandatory declassification" request, the Federation of American Scientists (FAS) said Monday.

From the first intercepted cable -- a 1945 message from Vietnamese leader Ho Chi Minh to his Russian counterpart Joseph Stalin -- to the final evacuation of US spies from Saigon, the 500-page report retold Vietnam War history from the perspective of "signals intelligence," the group said in a statement.