Pentagon investigates possible insider attack at Syria base

US previously believed attack at Green Village site that injured four American personnel was indirect fire

The US-led coalition strikes outside the town of Al Mayadeen in Deir Ezzor province, which it reported to be the source of an earlier attack on its Green Village base in north-east Syria. AFP

A recent attack on US military personnel in eastern Syria, which caused four to suffer traumatic brain injury, was intentional and not "indirect fire", the Pentagon said on Monday.

Pentagon spokesman John Kirby said at least one person had deliberately placed explosives near US troops.

There is "concern about some sort of insider threat" if it is now assumed that the attack was carried out through deliberately placed explosives, Mr Kirby said.

US Central Command earlier said the attack could have been indirect fire -- a military term that usually means a rocket attack or shelling -- but last week determined that the explosives had been planted in an ammunition depot and shower block. The incident is still under investigation, Centcom said.

Mr Kirby and the US-led coalition have not indicated who was responsible for the attack.

It is unclear if the incident was caught on video surveillance and there were no details of the number of people involved.

US troops were posted to Syria during the campaign against ISIS, in partnership with a Kurdish-led group called the Syrian Democratic Forces.

Iran-backed militias have established a foothold in Syria while fighting in support of President Bashar Al Assad during the country’s 11-year war.

While Iranian-backed forces have occasionally attacked US troops in Syria with rockets, ISIS militants could also be responsible for placing the explosives.

It raises the question of how secure the base is against the threat of insider attacks.

All four US personnel who were injured in the attack have resumed service or will soon return to duty and will be continually evaluated by medical personnel, Mr Kirby said.

Reuters contributed to this report