PARIS (Reuters) - Forces loyal to Syrian President Bashar al-Assad carried out a "massive and coordinated" chemical attack on Aug 21, according to a declassified French intelligence report released on Monday, a French government source told Reuters.

The nine-page document - issued by external and military intelligence services and to be presented to lawmakers later on Monday - lays out five points that suggest Mr Assad was behind the attacks.

"This poses a major threat to national and global security," the source said.

The intelligence includes satellite imagery showing the attacks coming from government-controlled areas to the east and west of Damascus and targeting rebel-held zones. The source said Mr Assad's forces had since bombed the areas to wipe out evidence.

"Unlike previous attacks that used small amounts of chemicals and were aimed at terrorising people, this attack was tactical and aimed at regaining territory," the source said.