The U.S.-led anti-Daesh coalition strikes on the forces allied to Syria's Bashar al-Assad regime on Tuesday were an "act of aggression", Russian foreign minister has said.
"Of course, this is an aggressive act that violates the sovereignty, territorial integrity of Syria," Sergey Lavrov said at a news conference with his Spanish counterpart Alfonso Dastis on Wednesday.
The U.S. Defense Department said on Tuesday the pro-regime forces posed a "threat" to the coalition and allied forces based at a garrison in the southeastern Syrian border town of at-Tanf as they violated what the coalition called a "well-established de-confliction zone".
Lavrov said "deliberately or not", the strikes aimed at the "most effective" forces fighting against terrorists on the ground, and was a "cause of concern".
Calling the declaration of a so-called "de-confliction zone" in Syria "illegitimate," Lavrov said he did not know anything about it. "This must be some territory, which the coalition unilaterally declared."
The minister added Russia, Turkey and Iran would continue to work on the details of the functioning of de-escalation zones in Syria.
On May 4, Moscow, Ankara and Tehran signed a deal in the Kazakh capital, Astana, to establish de-escalation zones in the war-torn country.
