A French intelligence report released Monday said there was "massive use of chemical agents" in an August 21 attack in Syria and that only the regime could have been responsible.
The report, made public after Prime Minister Jean-Marc Ayrault met with lawmakers, said the "Syrian regime launched an attack on some suburbs of Damascus held by units of the opposition, combining conventional means with the massive use of chemical agents."
It said that based on video reports, French intelligence had counted at least 281 dead but that reports of up to 1,500 killed were consistent with such heavy use of chemical weapons.
"The attack on August 21 could only have been ordered and carried out by the regime," the report said.
"We believe the Syrian opposition does not have the capacity to carry out an operation of such magnitude with chemical agents," it said.
The report said Syria "had one of the biggest operational stocks of chemical weapons," including an arsenal of more than 1,000 tons comprising sarin and mustard gas and more powerful neurotoxic agents.
Syrian President Bashar al-Assad's regime also had a range of Scud and other missiles capable of making chemical strikes over distances of up to 500 kilometers and an array of rockets and aerial bombs to launch such attacks, it said.
It said the attack combined ground strikes and chemical weapons "in a coherent tactical maneuver".
The French defense ministry will make six of the 47 videos filmed on morning of the attack available on the defense ministry's website from Monday evening, a government source said.
The source said the videos had been "authenticated" by the intelligence services and health and defense officials.
The source said separately that intelligence officials had concluded that rockets used in the attack were fired from regime-controlled areas.
"Imagery shows that the launch zone for the rockets was held by the regime while the strike zone was held by the rebels," the source said.