The U.S. State Department says it is "saddened and horrified" by the news of the “brutal murders” of seven rescue workers at their base in Syria’s rebel-held Idlib Province.
Spokeswoman Heather Nauert on August 13 condemned the attack by “cowardly acts of masked men” against the civilian volunteers.
The Syrian Civil Defense, known as the White Helmets, has been honored worldwide for efforts to rescue civilian victims of air attacks and artillery fire since 2013.
Officials reported that the seven volunteers were killed in their sleep on August 12 in the town of Sarmin in Idlib Province when unidentified assailants opened fire.
It was not immediately clear who was responsible for the killings.
Much of Idlib is controlled by Al-Qaeda-linked insurgents.
Syrian Civil Defense said two minibuses and other equipment was stolen after the attack.
Dozens of the first responders have been killed in the six-year Syrian civil war.
The group is funded through donations from several governments, including Britain, Germany, the Netherlands, and the United States.
The State Department statement praised the volunteers “who work tirelessly as first responders in order to save lives in incredibly dangerous environments.”