Islamic State gunmen on Wednesday publicly killed dozens of men belonging to a resistant Sunni tribe, witnesses said, in another chilling message to authorities seeking to galvanize opposition to the militants.

Social media accounts affiliated with the extremist group said the militants killed 46 tribesmen in the western city of Hit, which the Islamic State seized this month. Residents confirmed that the men — most of them members of the Albu Nimr tribe — were killed in a city square.

The tribesmen had been holding off Islamic State advances in and around Hit for months but lost the city amid complaints that they needed more support.

Enlisting Sunni tribes such as the Albu Nimr in the fight against the Islamic State is a critical component of the Iraqi and U.S. strategy against the militants in the western province of Anbar, a key pathway to Baghdad. But the efforts have lacked coordination and organization.

The reported mass killing in Hit echoes the slaughter of about 700 members of the Shaitat tribe across the border in Syria in August after they rose up against the extremists.

The Islamic State began arresting men from the Albu Nimr tribe shortly after the militants took control of the city, said a 32-year-old resident who spoke on the condition of anonymity for security reasons.

He said dozens of tribesmen had already been killed in Islamic State prisons before Wednesday’s slayings. Tribal leaders had negotiated for 57 bodies to be returned for burial in past weeks, he said, but the arrests of tribesmen continued.

“Then they gathered them in al-Bakir Square at 11 a.m. today, hands bound, and shot them all,” the resident said. He claimed to have twice counted the men lined up and put the number killed at 47.

A member of the tribe, who also declined to be named for security reasons, said his 42-year-old brother was among those killed. He had been missing for four days.

“I saw my brother among them,” the tribesman said. “They shot my brother in front of me.”

Pictures distributed on pro-Islamic State social media accounts showed bodies lined up on the pavement.

The militant group’s supporters accused the men of being members of the Sahwa, or Awakening, movement, the U.S.-backed program that helped turn tribal leaders against al-Qaeda in the years before the U.S. withdrawal from Iraq.

Prime Minister Haider al-Abadi has been attempting to reach out to Iraq’s Sunni tribes for support.

“There are people who are ready to fight,” said Gen. Hassan Dulaimi, a former deputy police chief in Ramadi, who is working with the tribal forces battling the militants. “We just need help to do that.”