Fourteen EU ministers called Wednesday for a ceasefire in the Syrian province of Idlib, where hundreds of thousands have been displaced by a Russian-backed Syrian offensive against rebels supported by Turkey.
The violence in Syria's last rebel-held enclave has caused a humanitarian crisis and sparked tensions between Ankara and Moscow.
French Foreign Minister Jean-Yves Le Drian, his German counterpart Heiko Maas and the foreign ministers of 12 other EU countries warned that what Moscow has presented as a fight against terrorism did not justify "massive violations of international humanitarian law".
In an open letter published in French daily Le Monde, the ministers urged the Syrian regime and Moscow to "immediately end hostilities" and negotiate with Turkey "to achieve a de-escalation."
Russia and Turkey in 2018 agreed to create a demilitarised zone in Idlib but the accord has fallen apart as Syrian President Bashar al-Assad's forces move to recapture the last big region beyond his control.
Turkish President Recep Tayyip Erdogan on Wednesday vowed he would not take the "smallest step back" in the stand-off with Damascus and Russia.
A day earlier, Russian Foreign Minister Sergei Lavrov rejected calls for a halt to the Russian-backed incentive, saying it would be tantamount to "capitulating before terrorists."
The 14 ministers said they were "perfectly lucid about the presence of radical groups in Idlib" but said this did not justify "incessant airstrikes and the dropping of barrel bombs".
French President Emmanuel Macron and German Chancellor Angela Merkel have called for summit with Erdogan and Russian President Vladimir Putin to seek an end to the crisis.
Erdogan on Saturday announced a four-way summit on March 5 but later said there was "no full agreement" on the meeting.