Pressure is mounting on the United Nations to take action against the Syrian regime after a chemical attack on Tuesday in central Syria left scores of civilians dead.
Western powers are demanding an investigation into the killings in Khan Sheikhun, Idlib province, and want action taken if Damascus is found to be responsible for the Sarin chemical attack.
France said it would pursue a UN Security Council resolution to investigate the killings, which left 86 people dead including at least 20 children.
A resolution presented by the UK, France and US demanded action following the attack.
"These crimes must not go unpunished," Ayrault told CNEWS television.
"It's difficult because up to now every time we have presented a resolution, there has been a veto by Russia and sometimes by China... but we must cooperate because we need to stop this massacre."
US ambassador to the UN Nikki Haley has meanwhile warned that Washington might carry out unilateral action against Damascus if the UN did not act collectively.
The draft UN resolution put forward by Western nations would see Organisation for the Prohibition of Chemical Weapons' investigators probe the killings with the regime required to cooperate.
One potential hurdle is veto carrying Security Council member Russia, a key supporter of the regime and said to be behind the bombing of a hospital used to treat the chemical attack survivors following the attack.
Moscow has continued to back its Damascus ally, claiming it had no "objective" data that the regime was culpable.
Damascus has meanwhile claimed that its war planes struck a "chemical storage" facility, although most experts have rubbished these claims.
Syria officially relinquished its chemical arsenal and signed the Chemical Weapons Convention in 2013.
This followed another deadly chemical attack in the opposition town of Ghouta, which led the US and its allies to threaten Damascus with military action.
Evidence is mounting that the regime carried out Tuesday's killings.
Turkey said that autopsies of three Syrians killed pointed to Bashar al-Assad's regime launching the Sarin chemical attack.
"Autopsies were carried out on three of the bodies after they were brought from Idlib. The results of the autopsy confirms that chemical weapons were used," Justice Minister Bekir Bozdag said according to Anadolu news agency.
"This scientific investigation also confirms that Assad used chemical weapons," Bozdag added.
The scale of the killing has led to US President Donald Trump make an apparent u-turn on his Syria policy calling the attack an "affront to humanity" and promising action.
"I will tell you, it's already happened, that my attitude towards Syria and Assad has changed very much," Trump said.
Turkish President Recep Tayyip Erdogan meanwhile blasted the Syrian regime for the attack.
"Hey murderer Assad, how are you going to escape from [the victims'] curse?" Erdogan said.
Other nations have also backed the view that the Syrian regime is responsible, while independent researchers and experts also say Damascus was behind the attack.
Khan Sheikhun is still reeling from the devastating attack, with dead animals lying in the streets and residents still shell-shocked after watching their entire families die, according to an AFP correspondent in the town.
"Nineteen members of my family were killed," 28-year-old Abdulhamid said in the town, surrounded by mourning relatives.
"We put some masks on but it didn't do anything... People just started falling to the ground," said Abdulhamid, who lost twin children and a wife in the attack.
Agencies contributed to this story.
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