As extremist rebels in Syria lay claim to fresh weapons, a new video circulating online purports to show an al-Qaeda-linked group fielding U.S.-supplied anti-tank weapons that may have been intended for more moderate factions in the conflict.

In early November, the al-Qaeda-linked Jabhat al-Nusra ousted two U.S.-supplied moderate factions, Harak Hazam and the Syrian Revolutionary Front, from their strongholds in northern Idlib province. Although al-Nusra was thought to have seized significant caches of equipment during the fighting, the exact nature of those arms has been unclear.

On Monday, however, a Twitter account associated with Jabhat al-Nusra posted a photo of a TOW anti-tank guided missile system, a formidable weapon used against armored targets. […]