The U.S. called on the Syrian regime and its allied forces Monday to immediately halt all hostilities in northwestern Syria's Idlib province after an airstrike on a Turkish convoy killed three civilians and injured 12 others.
"The Assad regime and its allies must return to the ceasefire in #Idlib now," State Department spokeswoman Morgan Ortagus said on Twitter.
"Today’s reckless airstrike on a Turkish convoy follows ongoing vicious attacks against civilians, humanitarian workers, and infrastructure. We condemn this violence and it must end."
Earlier Monday, a troop transfer to Idlib was initiated by the Turkish military to ensure the safety of an observation post, to keep supply routes open and prevent civilian casualties in the region, according to Turkey's Defense Ministry.
The ministry strongly condemned the airstrike, saying it "violates existing agreements, cooperation and dialogue with Russia".
Turkey and Russia agreed last September to turn Idlib into a de-escalation zone where acts of aggression are expressly prohibited.
The Syrian regime and its allies, however, have consistently broken the terms of the ceasefire, launching frequent attacks inside the area.
The de-escalation zone is currently inhabited by about four million civilians, including hundreds of thousands of people displaced by regime forces from cities and towns throughout the war-weary country.
Hundreds of thousands of people have been killed and more than 10 million others displaced during the course of Syria's more than eight-year conflict, according to the UN.