AMMAN - The US military said it had shot down an armed, Iranian-made drone that had been bearing down on its forces near a garrison in Syria's southeast on Tuesday, in the latest sign of increasingly frequent confrontation with Damascus and its allies.

Russia accused the US-led coalition of "complicity with terrorism" after the drone was downed.

The incident closely followed Sunday's US downing of a piloted Syrian army jet in the Raqqa countryside.

That was a rarity in modern warfare, representing the first time the US Air Force had downed a manned jet since 1999.

In the latest incident, the Pentagon said a US F-15E Strike Eagle jet flying over Syrian territory fired on the Shahed-129 drone after it displayed hostile intent and advanced on coalition forces.

Pentagon spokesman Navy Captain Jeff Davis said it had "dirty wings", meaning it was armed.

"I can tell you it was an Iranian-made drone," Davis said, declining to speculate on who specifically was operating it.

The area falls in a part of Syria that was recently identified as a military priority by Damascus, and is seen as strategically important for Iran as it seeks to secure a land corridor between forces it supports in Syria and Iraq.

Russian warning

Russia has issued a warning of its own to the United States in response to the downing of the Syrian jet, saying on Monday it would view as targets any planes flying west of the Euphrates River, though it stopped short of saying it would shoot any down.

Still, the Pentagon said it had not seen hostile action by Moscow. "Public statements aside, we have not seen the Russians do any actions that cause us concern. We continue to operate, making some adjustments for prudent measures," Davis said.

Meanwhile, the US and Russian militaries swapped accusations about an unsafe intercept involving a US spy plane and a Russian fighter jet over the Baltic Sea.

In Syria's tangled conflict, Washington backs a coalition of rebel forces fighting the government troops and extremist militants. More than 320,000 people have been killed since Syria's conflict began in 2011.

Reuters - afp

The US-led coalition said on Tuesday that it had killed IS's self-proclaimed top cleric, Turki Binali, in an airstrike in May on the Syrian town of Mayadeen near the Iraqi border.

It described Binali as "a close confidant" of IS leader Abu Bakr al-Baghdadi, and said he "had a central role in recruiting foreign terrorist fighters and provoking terrorist attacks around the world".