USA warplanes have struck pro-Syrian government forces that were said to pose a threat to American troops and allied rebels operating near the border with Jordan.
A USA aircraft struck pro-Assad forces military vehicles in Syria Thursday near al-Tanf in southern Syria.
Russia also criticized the strike, with Deputy Foreign Minister Gennady Gatilov Gatilov accusing the USA on Friday of violating Syria's sovereignty and alleging the airstrike hit civilians, according to Russian media.
The strike took place after the convoy violated a de-confliction zone near the Jordanian border.
We are not increasing our role in the Syrian civil war, he said.
This was the third attack by American forces against Assad's military in recent months, The New York Times reported. If that's the case, it might be an isolated incident, but it shows how easily the US can be pulled into a new conflict because of its support for opposition groups inside Syria and the decision to expand the unauthorized war on ISIS into Syria.More news: Experts question North Korea role in WannaCry cyberattack
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The official statement said that Russian Federation had made "apparent" attempts to "dissuade Syrian pro-regime movement south toward At Tanf", but that those efforts were "unsuccessful".
Coalition forces have operated in the al Tanf area for many months training and advising vetted partner forces who are fighting ISIS.
"Such actions that were carried out against the Syrian armed forces. this is completely unacceptable".
Two US aircraft were dispatched as a "show of force" to get the Syrian vehicles to turn around, according to a US official.
Also on Thursday, Daesh "Islamic State militants" shelled a regime-controlled area in the city of Deir al-Zour in eastern Syria, killing 14 people and wounding 21 others, the Observatory said.
"This is not only an attack in Syria and against Syria, but also against Geneva [negotiations]".
Russian Federation supports the ceasefire in Syria while the U.S. weakens the effort fighting against terrorist groups, he added. An earlier chemical weapons attack that killed more than 80 civilians is thought to have been launched from there.