TOPSHOT - Armed men in uniform identified by Syrian Democratic forces as US special operations forces ride in the back of a pickup truck in the village of Fatisah in the northern Syrian province of Raqa on May 25, 2016. 
US-backed Syrian fighters and Iraqi forces pressed twin assaults against the Islamic State group, in two of the most important ground offensives yet against the jihadists. The Syrian Democratic Forces (SDF), formed in October 2015, announced on May 24 its push for IS territory north of Raqa city, which is around 90 kilometres (55 miles) south of the Syrian-Turkish border and home to an estimated 300,000 people. The SDF is dominated by the Kurdish People's Protection Units (YPG) -- largely considered the most effective independent anti-IS force on the ground in Syria -- but it also includes Arab Muslim and Christian fighters.

 / AFP / DELIL SOULEIMAN        (Photo credit should read DELIL SOULEIMAN/AFP/Getty Images)
CIA Director's grave warning: ISIS as dangerous as ever
02:23 - Source: CNN

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The troops were lightly wounded on June 9

The administration hasn't publicly revealed the incident

CNN  — 

Four U.S. military advisers were lightly wounded earlier this month in northern Syria by attackers who were believed to be part of ISIS, CNN has learned.

The Pentagon has not yet spoken publicly about the June 9 incident, but several defense officials told CNN it happened when an anti-tank round was fired close to the advisers’ position and exploded a vehicle near them.

The troops suffered light shrapnel wounds and are believed to have returned to duty. The officials also did not immediately know if the troops involved returned fire at the attackers.

While the attackers are believed to be ISIS, the U.S. military is not certain of their identity.

The administration’s official policy is that U.S. troops are in Syria and Iraq for training, advising and assisting local forces, but that their role is not to engage in combat. They have returned fire when attacked, and have in the past moved in to assist local forces when they are under fire.

On at least five occasions, American troops have either been wounded or killed in Iraq and Syria when faced with enemy fire while training and assisting U.S.-backed forces.

The Pentagon generally does not publicly disclose when troops are wounded, officials said. Because these incidents mainly involve U.S. special operations forces, the military does not want to disclose the specific locations in which they are operating, in hopes of keeping their locations secret from ISIS.

However, when troops are killed in action, there are policies that require the Pentagon to disclose the name of the killed service member and the location where it happened.

Defense officials also said they do not disclose specific information about the health status of individual troops who have been wounded due to privacy concerns. And the officials said they may not know of every incident in which troops fire their weapons at attackers because some incidents may not rise to the level of importance of being reported to the Pentagon.