US airstrikes in Syria killed dozens of civilians in a predominately Arab-populated village in the eastern part of Aleppo province Friday. The death toll was still rising as more bodies were found and missing family members were accounted for.

Initial reports had put the number of deaths at 52, but at least one US media outlet, McClatchy News Service, said it had obtained a list of 64 dead from ten families. Whatever the final figure, it is the worst atrocity perpetrated by the US-led campaign of bombing supposedly directed at Islamic State of Iraq and Syria (ISIS).

According to the Syrian Observatory for Human Rights, which has long supported the US-backed campaign to overthrow Syrian President Bashar al-Assad, at least nine children were among the victims of the US airstrike on the village of Bir Mahali. It described them as victims of a “massacre committed by the US-led coalition under the pretext of targeting the Islamic State.”

The group had previously downplayed civilian casualties in Syria, claiming that only 60 civilians had died in the hundreds of airstrikes by warplanes of the United States, Saudi Arabia and the other Gulf sheikdoms participating in the war against ISIS.

The US Central Command, which regularly reports US airstrikes in Syria and Iraq without any detail on the death toll or the exact targets struck, said the May 1 attack was among nearly a dozen in “the area of” Kobani, the largely Kurdish-populated town on the Syrian border with Turkey that became the focal point for US air strikes last fall. Bir Mahali is 33 miles south of Kobani.

McClatchy said that US warplanes had become involved in longstanding ethnic conflicts between Arabs and Kurds in the Euphrates River valley, an area with a mixed population that also includes Assyrians and other Christians. It cited reports from “activists pointing out that the fishing and farming village of about 4,000 Arabs has had tense relations with Kurds living nearby—especially with the Kurdish ‘People’s Protection Units’ or YPG.”

The implication was that Bir Mahali was targeted, not because of the presence of Islamic State forces—it is not clear whether there were any in the village—but because the Kurdish militia wanted to wreak havoc on an Arab-populated town.

The US military worked with the YPG in the months-long siege of Kobani. The YPG has political ties to the PKK, the Kurdish nationalist guerrilla force that has fought inside Turkey for decades, and is on the US State Department’s list of “terrorist” organizations.

The US-YPG connection demonstrates yet again that Washington uses the term “terrorist” in a completely cynical fashion, branding groups because they oppose US foreign policy, or fight US client states, not because of the methods they employ. When it comes to violence against civilians, as the atrocity in Bir Mahalli demonstrates, the US government is the world’s foremost practitioner of terrorism.

A statement from the Combined Joint Task Force, the official name for the US-led coalition bombing ISIS targets in both Iraq and Syria, said that there were 24 airstrikes carried out on May 1-2, of which 17 were in Syria, hitting Raqqa, the lone provincial capital under ISIS control, as well as targets near Kobani, Al Hasakah and Dair Az Zawr.

The seven airstrikes in Iraq were near Mosul, Tal Afar, Baiji, Ramadi and Fallujah, the five cities controlled by ISIS either wholly or in part.

The US military did not admit the killing of a large number of civilians in Bir Mahalli, but said it was investigating claims. Major Curtis Kellogg, a military spokesman, told the Associated Press, “We currently have no information to corroborate allegations that coalition airstrikes resulted in civilian casualties,” adding, “Regardless, we take all allegations seriously and will look into them further.”

The reported mass killing of civilians in Syria comes amid indications that key US client states in the region, including Saudi Arabia and Qatar, are stepping up their support for anti-government “rebels” fighting the Assad government.

The Washington Post reported April 30,

“The delivery of additional weapons and financial aid from Saudi Arabia, Turkey and Qatar have facilitated recent advances against government forces in northwest Syria by the Army of Conquest, a newly formed umbrella of diverse rebel groups, including al-Qaeda’s affiliate and other Islamist groups, along with ‘moderate’ [i.e., pro-US] fighters.”

Last month these forces captured the northwestern provincial capital Idlib, and then the city of Jisr al-Shughur, as well as numerous bases and outposts of the Syrian army, in an offensive that threatens to cut off the capital city, Damascus, from the Mediterranean coastal region that is Assad’s political stronghold. Jabhat al-Nusra, the al Qaeda affiliate in Syria, has played a major role in this military push.

The Post also reported that at a meeting of the anti-ISIS coalition in early April, hosted by Jordan, “administration officials were bombarded with questions about US leadership of the 60-nation group, and how it would address the global expansion of the Islamic State.”

The New York Times, reporting on the same meeting, said that members of the US-led coalition were pressing Washington “to agree to a broadening of the campaign to include terrorist groups that have declared themselves to be ‘provinces’ of the Islamic State.”

This could include extending the military operation to include targets in Libya, where ISIS is alleged to support Ansar al-Sharia, a local Islamist formation, as well as unspecified measures against supposed ISIS supporters in “Jordan, Lebanon, Saudi Arabia, Tunisia and Yemen, according to American counterterrorism officials.”