The U.S. military's Central Command said the drone shot down Tuesday was a Shaheed 129 and appeared to have been operated by "pro-regime" forces, a term which U.S. officials previously have used to describe Hezbollah elements.
"As a precautionary measure, Australian Defense Force [ADF] strike operations into Syria have temporarily ceased", the Defense Ministry statement said.
Sunday's downing of a regime plane and an incident this month when an American jet shot down a pro-regime drone illustrate the line's limitations. The Russian-US communication channel to prevent mid-air incidents over Syria is in operation, a spokesman for the headquarters of Operation Inherent Resolve, which is being conducted in Iraq and Syria by a group of countries led by the US, informed TASS on Tuesday.
The Russian defense ministry said in a statement that, starting today, it will track all jets and drones of the US -led coalition west of the Euphrates and treat them as targets.
"ADF are closely monitoring the air situation in Syria and a decision on the resumption of ADF air operations in Syria will be made in due course", the spokesman said.
That drone was shot down after it dropped one of several weapons it was carrying near a position where coalition personnel are training and advising partner ground forces in the fight against ISIS.
"There has been neither a [UN] Security Council decision, nor a request from the official authorities of the Syrian Arab Republic as a sovereign state" for such forces, he told Russia's Interfax news agency.
On Sunday, U.S. military said it shot down the Syrian SU-22 plane in self-defense and after contacting Russian counterparts through the established de-confliction line.
A US warplane on Tuesday shot down an armed drone linked to Syrian regime forces, the latest in a series of clashes between USA -backed forces and the regime of Bashar Assad that risks drawing American forces deeper into the conflict.
On Monday, Russia's defense ministry effectively drew a line across Syria west of the Euphrates River, saying that "all kinds of airborne vehicles, including aircraft and UAVs of the global coalition. will be tracked by the Russian SAM systems as air targets". Is it just rhetoric or does Moscow want to deny certain areas of Syrian airspace to US-led coalition aircraft?
The drone was thought to be armed and threatening U.S. troops on the ground, officials said.
The parties have avoided any direct military engagement during the years of civil war - similar to the numerous "proxy wars" during the Cold War phases, where US-Soviet interests were repeatedly in conflict but avoided direct declarations of war between the two super-powers.
But his remarks came amid questions whether the strike had been effective. It is still unclear what the missiles struck, and Iran has provided few details.
The US-led coalition said Tuesday that it had killed IS's self-proclaimed top cleric, Turki Binali, in an air strike in May on the Syrian town of Mayadeen near the Iraqi border.
On Sunday, Iran's Revolutionary Guards said they had fired mid-range ground-to-ground missiles from a site in western Iran targeting "the headquarters and meeting place and suicide vehicle assembly line" of "IS terrorists" in Deir al-Zour province.