France's foreign minister on Wednesday demanded that all Iranian-backed militia, including Lebanon's Hezbollah, leave Syria and said that Turkey and Iran were violating international law through their actions in the country.
Speaking on BFM television, Jean-Yves Le Drian also said there were indications Syrian government forces were using toxic gas against civilians although the U.N. would need to confirm that.
Asked whether he wanted Turkish armed forces to withdraw from Syria, Le Drian replied that he wanted "the withdrawal of all of those who ought not to be in Syria, including Iranian militia, including Hezbollah."
While not specifically calling for Turkey to pull back from its offensive against Kurdish militias in northern Syria, he said that Ankara should not worsen the conflict.
"Ensuring the security of its borders does not mean killing civilians and that should be condemned. In a dangerous situation in Syria, (Turkey) should not add war to war."
International law "is being violated by Turkey, by the Damascus regime, by Iran and those who are attacking eastern Ghouta and Idlib", he said. His remarks amount to France's toughest line yet on Turkey's involvement in the Syrian conflict.
France has backed the Syrian opposition during the seven-year war and is part of the U.S.-led coalition fighting Islamic State militants.
Le Drian is due in Tehran on March 5 for talks over its ballistic missile programme, the nuclear deal agreed with world powers in 2015 and the role of Iran in the region at a time when the United States has put pressure on its European allies to toughen their stance on Tehran.
Iran is a key ally of the Syrian government in the seven-year civil war and it says it has no intention of withdrawing unless Syria requested it do so.
Le Drian also said it looked likely that President Bashar al-Assad's forces were using chlorine gas in their Russian-backed offensive on the rebel-held Idlib province and in the besieged enclave of eastern Ghouta.
"I'm speaking with a degree of caution because you have to be careful pending full documentation, but all the indications that we have show that at the moment chlorine is being used by the Syrian regime," Le Drian said, adding that the United Nations had opened an investigation.
French President Emmanuel Macron said in May last year that he had clear red lines on chemical weapons saying that "any use of chemical weapons would result in reprisals and an immediate riposte, at least where France is concerned."