The US-led coalition and its Syrian partner forces came under Islamic State attack at the At Tanf garrison in southern Syria, Central Command said on Monday.
A CENTCOM spokesperson said three “partner forces” died in the attack.
In a statement released on Sunday, the coalition said Islamic State initiated the attack with a vehicle bomb (VBIED) and 20-30 fighters, followed by a ground assault that included militants in suicide vests.
“Coalition and partner forces engaged and defended [against] the ISIS attack with direct fire” before destroying the vehicles and remaining fighters with “multiple coalition airstrikes,” the statement said.
Later, the coalition released a correction: The amended statement omitted the word engaged, saying “Coalition and partner forces defended against the ISIS attack with direct fire” before calling in the multiple airstrikes.
Update April 11
The Wall Street Journal reported on April 10 that IS militants who attacked the base wore uniforms similar to those worn by US-backed rebels. Some had M-16s and vehicles captured from rebels in previous battles.
“It was a coordinated, complex attack. Whether or not it was a one-off, we will have to see,” a US military military official said.
As the fight intensified, US special operations forces and rebel partners who had taken up positions outside the base returned to help repel the attack.
According to the WSJ, US forces last week pulled out of the At Tanf base, wary of a possible retaliatory strike by Syria or Russia. The move was one of several steps the US military took in Syria in the aftermath of the US missile attack on al-Shayrat airbase, itself a response to a suspected chemical weapons attack by the Syrian air force.
The US-led coalition also scaled back airstrikes in Syria. Officials told the WSJ it had temporarily curtailed offensive airstrikes but expected to soon return to normal operations.
On April 11, spokesperson for the US coalition Col. Dorrian told Grasswire US military forces are on heightened alert in Syria after cruise missile strikes against Shayrat airbase, and Islamic State militants attempted to infiltrate At Tanf garrison in the south.
At Tanf, also written Al Tanf, is a small base near where Syria meets Jordan and Iraq.
The base is in a sparsely populated desert area of Syria and is believed to have been visited on a number of occasions by special operations units as they, and the local partner forces, try to reduce Islamic State’s ability to operate within the desert south of Raqqa and Deir Ezzor.
In August, BBC obtained images from June showing UK special forces operating around the base.
Since November 2015, the base has been occupied by the New Syrian Army (NSyA), a small rebel force that reportedly receives US military training and equipment.
On March 5, 2016, the NSyA captured Al Tanf border crossing from Islamic State.
Islamic State launched a suicide attack in the area in May 2016 that reportedly caused a large number of casualties.
In June the NSyA’s base was hit by an airstrikes which killed two people and injured 18 others. Russia denied responsibility, although bomb fragments were later identified by Bellingcat as Russian RBK-500 cluster bombs.
The group later launched an offensive against Islamic State around Abu Kamal, but were repelled after initial gains.
According to some reports, NSyA disbanded in December and some of its members formed the Revolutionary Commando Army.