Russian and Syrian regime forces bombed U.S.-backed fighters Tuesday in villages near the Syrian city of al-Bab, a U.S. general said Wednesday, characterizing the incident as a likely mistake.

Army Lt. Gen. Stephen Townsend, who leads the fight against the Islamic State in both Iraq and Syria, told reporters Wednesday that he believes the pilots thought they were bombing militants, not the Syrian Democratic Forces that the United States trains and advises. U.S. forces, who were a couple of miles away to assist the Syrian fighters, called in the information and the Russians halted the airstrikes, Townsend said.

Russia denied any involvement in the bombings afterward, saying neither Russian nor Syrian aircraft were involved, according to the Kremlin-funded news agency RT. “Not a single” airstrike on the areas Townsend cited were carried out by the two militaries, Russian defense officials said in a statement. Russia often denies involvement in military operations despite evidence to the contrary.

Townsend said the bombings occurred south and east of al-Bab. Islamic State fighters had been in the area but had left to get away from advancing forces, including rebels backed by Turkey.

Read the whole story from The Washington Post.

Featured image courtesy of Reuters.