Syria on Friday condemned a US-led coalition strike on pro-government forces as a "brazen attack" and said it would "not be intimidated" after the surprise assault.
US-led warplanes carried out the Thursday strike in the east of the country against a convoy of pro-government forces headed towards a remote coalition garrison near the border with Jordan.
"On Thursday at 16:30, the so-called international coalition attacked one of the Syrian Arab Army's positions on the Al-Tanf road in the Syrian Badia region, producing a number of martyrs and causing material damage," a military source told Syrian state media.
"This brazen attack by the so-called international coalition exposes the falseness of its claims to be fighting terrorism," it added.
"The Syrian Arab Army is fighting terrorism on its territory, and no party has the right to determine the course of its operations," the source said.
"The Syrian Arab Army will... not be intimidated by the attempts of the so-called coalition to stop it from performing its sacred duties."
Syrian ally Russia also denounced the US-led strike as "unacceptable."
"Such actions that were carried out against the Syrian armed forces... this is completely unacceptable, this is a breach of Syrian sovereignty," deputy foreign minister Gennady Gatilov was quoted as saying by state-run RIA Novosti in Geneva.
In a statement, the US-led coalition said it had struck "pro-regime forces... that posed a threat to US and partner forces."
The coalition said the strike came after unsuccessful "Russian attempts to dissuade Syrian pro-regime movement" as well as "a coalition aircraft show of force, and the firing of warning shots."
Syrian state media gave no precise toll in the attack, but the Syrian Observatory for Human Rights, a Britain-based monitor, reported eight killed "most of them non-Syrian."
An array of regular and irregular forces are battling alongside the government against rebels, including Russian and Iranian soldiers, and militants from Iraq and Lebanon's Hezbollah group.
The Thursday strike comes in the context of growing tension over which forces will take on the Islamic State group in Syria's east.
President Bashar al-Assad's army is trying to prevent US-backed forces from leading that fight.