A Syrian military source said rebels are making heavy use of U.S.-made anti-tank missiles paid for by Saudi Arabia and supplied via Turkey in recent weeks and the weapons are having an impact on the battlefield. The so-called TOW missile is the most potent weapon in the arsenal of rebel groups battling President Bashar Assad, and has been seen in action more frequently since Russia intervened with air strikes on Syria on Sept. 30. A rebel group was shown using one of the guided missiles to destroy a grounded Russian helicopter in Syria Tuesday. Addressing the increased supplies of TOW missiles for the first time, the Syrian military source said they had an impact on the fighting, but played down their overall significance, saying the army was gaining ground. "Through the course of the battles it became apparent that the terrorists have a bigger quantity of American anti-armor TOW weapons. They started using this weapon intensively," said the source. The Syrian government describes all the insurgents fighting it as terrorists. "This weapon, TOW, of course affects the work of the armored divisions. Certainly, it is a well-known American weapon whose impact is known: it is effective against armored vehicles," the source said. "They use it heavily which indicates this weapon has become available to them." The comments are a further indication of how increased military support for rebels from Assad's foreign enemies has helped the them confront a major, multi-pronged attack by the Syrian government and its allies Russia and Iran.