Sarin or a similar banned toxin was used in an attack in Syria's Idlib province on April 4 that killed nearly 90 people, the global chemical weapons watchdog says.
The finding supported earlier testing by Turkish and British laboratories.
The Organisation for the Prohibition of Chemical Weapons' Director General Ahmet Uzumcu said on Wednesday results of the analysis "indicate that sarin or a sarin like substance was used".
The finding was based on tests on bio-medical samples collected from three victims during their autopsies that were analysed at two OPCW-designated laboratories, the OPCW said.
"Bio-medical samples from seven individuals undergoing treatment at hospitals ... (also) indicate exposure to sarin or a sarin like substance," the statement said.
Earlier French Foreign Minister Jean-Marc Ayrault said intelligence services will provide proof in the coming days that Syrian President Bashar al-Assad's forces used chemical weapons in an attack on April 4.
"There is an investigation underway (by) the French intelligence services and military intelligence ... it's a question of days and we will provide proof that the regime carried out these strikes," Ayrault told LCP television on Wednesday.
"We have elements that will enable us to show that the regime knowingly used chemical weapons," he said.
