Online videos show Syrian rebels using what appear to be U.S. anti-tank rockets, weapons experts say, the first significant American-built armaments in the country’s civil war.

The rebel faction shown operating the U.S. missiles in the first videos, a relatively secular and moderate group called Harakat Hazm, declined to comment.

The Syrian activist, who identified himself as Samer Mohammad, said Harakat Hazm received 10 anti-tank missiles earlier this month near Aleppo and Idlib, two cities torn by heavy fighting near the northern border with Turkey.

He said Harakat Hazm had launched five of the rockets to destroy four tanks and win a battle in the Idlib suburbs of Babolin and Salhieh, and this was the first time such U.S. arms had figured in Syria’s fighting.

Western states have long been reluctant to make good on repeated talk of supplying weapons to Assad’s foes, nervous of arms falling into the hands of jihadi militants or simply abetting more bloodshed in a conflict that has killed over 150,000 people and displaced millions over the past three years.