The tribesmen later withdrew from the villages after coming under heavy shelling and Russian air attacks.

“Fighting began at dawn. [It involved] Syrian tribesmen, most of whom had taken part in the Syrian revolution and who are now dissatisfied with the SDF rule in Deir Az Zor,” local media activist Ramadan Suleiman told Al Jazeera on Friday.

The SDF controls a semi-autonomous Kurdish-ruled zone in Syria’s northeast, which includes large parts of Deir Az Zor province and stretches into parts of Aleppo in the northwest.

The tribesmen who participated in the fighting in Aleppo had been based in areas under the control of the Syrian opposition in Aleppo and neighbouring Idlib province, but some originally came from Deir Az Zor before being displaced in the war.

“Three villages were liberated, and two are under the control of tribesman” north of the city of Manbij in Aleppo’s eastern countryside, Suleiman said before the fighters withdrew.

Images shared on social media by fighters from the tribes reportedly showed the villages of al-Muhsinli and Arab Hassan as well as military sites belonging to the Syrian government under their control.

The images could not be verified by Al Jazeera.

However, local sources said that hours later, shelling from areas under the control of the SDF and the Syrian government as well as Russian air attacks forced them to withdraw.

The SDF, a United States-backed alliance of Arab tribesman and Kurdish fighters belonging to the Kurdish People’s Protection Units (YPG), had spearheaded the offensive that defeated ISIL’s (ISIS’s) self-declared “caliphate” in Syria in 2019.

But tensions between the tribesmen and the Kurdish fighters who lead the SDF escalated into violence on Sunday when the head of the Deir Az Zor Military Council, a local Arab armed group affiliated with the SDF, was arrested by the SDF, triggering fighting that has since killed dozens of people.

Ahmad al-Khabil, known as Abu Khawla, still remains in custody. He has been accused by the SDF of alleged involvement in “multiple crimes and violations”, including drug trafficking.

In an audio recording circulated on social media, Ibrahim al-Hafil, leader of the Akidat tribe, called upon all the Arab tribes in the region to unite against the SDF.

He also demanded the release of civilians detained by the organisation. Al-Hafil advocated for the establishment of a military council representing the Arab tribes in the region, independent of Kurdish control, with the US as its direct point of contact.

According to the Britain-based monitoring group, the Syrian Observatory for Human Rights, overnight fighting killed five supporters of Abu Khawla.

Their deaths bring the total number of people killed since the fighting broke out to 45, including five civilians and 17 SDF members, the observatory, which has a vast network of sources inside Syria, told the Agence France-Presse new agency.

On Friday, the US called for an end to the fighting, calling on “all parties to de-escalate and peacefully resolve the situation”.

“The violence in northeast Syria must cease,” said the US military’s Operation Inherent Resolve, which supports the fight against remnants of ISIL.

In a separate incident, five children were killed in artillery shelling from areas jointly controlled by the Syrian government and the SDF, the Syria Civil Defence said.

In a statement, Mounir al-Mustafa, the deputy director of the volunteer emergency services group, also known as the White Helmets, said the Syrian government targeted the Aleppo village of al-Mohsenli in the Jarabulus countryside, west of the Euphrates and just south of the Turkish border.

“The towns of Joseph, Maaratah and al-Fatira in Bel Al-Zawiya, south of Idlib [city], were also subjected to artillery shelling,” he said, adding that there were no casualties in those areas.

“These attacks multiply the suffering of civilians and are considered a clear violation of international humanitarian law,” he said. “As the international community fails to hold the perpetrators accountable, civilians are left unprotected under their blows without finding a safe haven to protect them.”

Additional reporting by Ali Haj Suleiman in northwest Syria.