US-led coalition jets have launched air strikes in Syria, hitting convoy of Syrian and Iranian-backed militias that were heading towards the Tanf base in southern Syria where USA special forces are based, reports say.
It's been publicly known for almost a year that US special operations forces operate out of the base, near where the borders of Jordan, Iraq and Syria meet, training Syrian rebels in their fight against Islamic State militants.
Aircraft of the US-led global coalition fighting the ISIS terrorist group have bombed a convoy of a militia supporting the regime of Syrian President Bashar al-Assad in the ongoing civil war in Syria.
"The Syrian Arab Army is fighting terrorism on its territory, and no party has the right to determine the course of its operations", the Syrian military source added.
"We are deeply anxious about the erosion of the emerging understanding of the need to combine efforts of all those who confront terrorists" such as the IS and al-Qaida's branch in Syria, Lavrov said.
They are gathering intelligence, including the location of British foreign fighters for the RAF to kill, as well as training moderate Syrian rebels.
Mattis said he believed the Iranian-directed forces moved into the zone against the advice of Russian Federation but that he was unable to confirm that with certainty.
"We are not increasing our role in the Syrian civil war, but we will defend our troops", Mattis said.More news: USA launches NAFTA renegotiation countdown
Describing the hours-long event as an "escalation-of-force situation", the official said it did not signal a strategic shift for the coalition, which remains focused on fighting IS group.
The strike was near a base in An Tanf, which is used by the coalition to train vetted Syrian opposition to help fight against Isis.
A State Department spokeswoman said on May 17 that the US would continue to pressure the Russian government to drop its support of the Assad regime.
The Syrian army had been sending reinforcements in the last few weeks to the desert region near its border with Iraq and Jordan.
The airstrikes were characterized to reporters as a "defensive", targeting militia fighters "advancing well inside an established de-confliction zone", northwest of the At Tanf, CENTCOM said in a statement.
His comments echoed an earlier statement by a deputy, Gennady Gatilov, who said the coalition's strikes on Syrian forces were "unacceptable" and could hinder peace talks.
Russian Federation supports the ceasefire in Syria while the United States weakens the effort fighting against terrorist groups, he added.