A U.S. fighter jet operating in Syria destroyed a Russian-built tank over the weekend in an act that officials described as self-defense.

Fox News' Lucas Tomlinson first reported the destruction of the tank, noting that the tanks' three-man crew were all killed in the strike inside. What makes this incident noteworthy is the fact that it is unclear who was operating the tank, whether it was the Syrian government, forces loyal to the Syrian government, or members of the Russian military.

"The tank had been maneuvering with coordinated indirect fire on a defensive position occupied by Syrian Democratic Forces and Coalition advisers," U.S. Marine Corps Maj. Adrian J.T. Rankine-Galloway told Business Insider.

The tank was reportedly destroyed after "pro-regime forces" launched an attack on U.S. special forces last week, which prompted the U.S. to respond "with a furious barrage of air and artillery strikes and reported killing 100 pro-government troops, but sources told Bloomberg on Saturday that as many as 200 or 300 Russian mercenaries were killed in the attack."

Business Insider further notes that the U.S. military has established lines of communication with the Russian military in an effort to avoid any military confrontations that could escalate into a full-blown war between the two military powers.