Smoke rises from the Syrian city of Manbij. Photo: AP

On Wednesday, the U.S. military announced that it was pursuing a formal investigation into the July 19 airstrike in a northern Syrian city that observers estimate killed at least 73 civilians. A subsequent airstrike in the same city “may have resulted” in yet more civilian casualties, Centcom disclosed late Thursday.

“U.S. Central Command initiated an assessment following internal operational reporting that a strike today near Manbij, Syria may have resulted in civilian casualties,” the military said in a statement. “We can confirm the Coalition conducted airstrikes in the area in the last 24 hours.”

The airstrikes took place around the strategically-critical city of Manbij, where clashes between U.S.-backed Syrian militants and Islamic State fighters have dragged on for months. Local and outside activists described the horrific aftermath of a coalition bombing run against the village of Tokkhar, outside Manbij, earlier this week.

“The death toll is 117. We could document [the identity of] 73 civilians including 35 children and 20 women. The rest of the dead bodies are charred, or have been reduced to shreds,” Adnan al-Housen, an activist from Manbij, told the Guardian. The Syrian Institute for Justice, a Turkey-based human rights group, also found that 73 civilians had been killed. Chris Wood, director of the U.K.-based AirWars, described it as “likely the worst reported civilian toll of any coalition attack since the bombing campaign against ISIS began nearly two years ago.”

At least 28 more civilians were killed in the latest incident, according to the Syrian Observatory for Human Rights, including women and children. “The death toll is expected to rise because there are some people in critical situation,” the Observatory said in a statement. The Guardian reports:

The Observatory said 13 others were killed in the airstrike. It is not known if those 13 are civilians or members of Isis, which has been fending off ground and air attacks for more than two months from the US and its Syrian allies.

US military officials have said they expect the battle for Manbij to drag on, as Isis has dug into a position both sides consider a critical buffer between US-backed forces and the Isis capital of Raqqa. Manbij has strategic value for another reason: it provides a pathway for Isis to exfiltrate fighters through Turkey to the outside world.

Syrian allies of the US, advancing through extreme fighting, have accumulated terabytes’ worth of digital information on Isis from computers and mobiles left behind in the battle.

“We take all measures during the targeting process to avoid or minimize civilian casualties or collateral damage and to comply with the principles of the Law of Armed Conflict,” Centcom’s statement on Thursday concluded.