It called on the U.N.to condemn the attack. "Only the regime has such air assets", said Ayrault. The US-led coalition had by then spent a year striking terrorist targets in Syria without approval by the country's government. The SDF and the Syrian government have largely avoided confrontations with each other over the course of the Syrian civil war.
He said the substance France believes was used in the attack contains hexamine, a component that was also found in a gas attack in northwest Syria in 2013. According to the French army, only the Syrian regime had helicopters so it had to be behind the attack.
The attacks came a day after Turkey conducted air strikes on Kurdish rebel positions in Syria and Iraq.
Assad has repeatedly denied that his forces used chemical weapons and claimed that evidence of a poison gas attack was made up. Lavrov says claims that the experts were warned by a United Nations body against traveling to the location because it's unsafe are "lies", adding that Moscow went back to the United Nations and found out that there was no such warning.
Tillerson visited Moscow earlier in April to meet Russia's Foreign Minister Sergei Lavrov and President Vladimir Putin.
Ayrault also said that French intelligence services showed that only Syrian government forces could have launched such an attack - by a bomber taking off from the Sharyat airbase.
The attack has been widely blamed by Western powers on the Syrian government, which is supposed to have given up its chemical weapon stockpile in 2013 following an attack in the Ghouta area of Damascus that activists say killed 1,400 people.
The attack in the town of Khan Sheikhoun killed scores of people and prompted the United States to launch a cruise missile strike on a Syrian air base in response, its first direct assault on the Assad government in the conflict.
Analysis by French experts of samples from the April 4 attack site and the blood of one of the victims confirmed the use of Sarin, its report said.
"The Kremlin thinks as before that the only way to restore the truth of what happened in Idlib is impartial worldwide investigation".
Russian Federation has previously called for an worldwide probe, and Peskov expressed regret that the Organization for the Prohibition of Chemical Weapons, or OPCW, has turned down the Syrian government's offers to visit the site of the attack and investigate. It also denies it has any chemical weapons. Since its inception, the organization has overseen the destruction of some 95 percent of the world's declared stocks of chemical weapons.
"We know, from a certain source, that the process of fabrication of the samples taken is typical of the method developed in Syrian laboratories", Foreign Minister Jean-Marc Ayrault told reporters after presenting the findings to the cabinet.
"This (production) method bears the regime's hallmarks and allows us to determine its responsibility for this attack", he said.
The Organisation for the Prohibition of Chemical Weapons (OPCW) said on April 19 that sarin or a similar banned toxin was used in the Khan Sheikhoun attack, but it is not mandated to assign blame.
Lavrov told a security conference in Moscow the US response "pushes the prospect for a wide worldwide front on terror even further away".