France's military deliberately exposed soldiers to a nuclear test in the Sahara Desert to study how the atomic bomb would affect their bodies and minds, it was reported.
Reacting to the report in Le Parisien newspaper, which cited a secret defence document, the government pledged full transparency.
Defence minister Herve Morin denied that soldiers in the April 25, 1961 operation were used as human guinea pigs, but said "it is obvious that today nobody would carry out tests in such conditions".
In total, France conducted 210 nuclear tests, both in the atmosphere and underground, in the Sahara Desert and the South Pacific from 1960-1996. After decades of pressure from victims, the government finally agreed last year to compensate them.
Le Parisien said it had obtained a 260-page confidential document summarising France's nuclear tests in the Sahara, including the April 25 1961 above-ground test, which was codenamed "Gerboise verte" or green gerbera.
The military document, drawn up in 1998, said the test was designed to "study the atomic weapon's physiological and psychological effects on man, to obtain elements necessary to prepare them physically and morally for modern combat", Le Parisien said.
According to the newspaper, the military document said 300 soldiers took part in a ground exercise coinciding with the blast.
The defence report said soldiers emerged from their shelters 20 minutes after the explosion "and looked with apprehension at the cloud", Le Parisien said. Soldiers on foot advanced toward the epicentre, stopping 700 meters away, the report said. Armoured reconnaissance vehicles advanced to 275 meters from the site.
The men wore gas masks, but military officials concluded that such protection slowed down manoeuvres and decided that in the future, foot soldiers should replace them with simple anti-dusk masks, Le Parisien said.
Asked if the soldiers were used as human guinea pigs, the defence minister said: "No."
"We have to stop analysing history with our 2010 vision," he told reporters. "We probably have to accept that errors were committed, at least about the consequences we should have taken."
For decades, the government refused to bow to pressure from people made ill by radiation. As recently as 2003, then-President Jacques Chirac said during a visit to Tahiti that tests had shown no ill effects to health from France's nuclear detonations in Polynesia.
Government spokesman Luc Chatel promised that more scientific data about France's nuclear testing would be disclosed.
"There is a desire for transparency on the part of the government, and it's the first time that's the case," he said.
France's parliament last year passed a law to compensate victims who acquired health problems following the tests, with sums to be decided on a case-by-case basis.
Jean-Paul Teissonniere, lawyer for the Associations of Veterans of Nuclear Tests in Polynesia and Algeria, said the report should be taken into account as officials decided how exactly to apply the law on compensation.
The report "is extra information," he said. "The Defence Ministry has been hiding things from us."