A source close to the SNA told the website that the Turkish-backed group opened the crossing to avoid accusations that it was preventing the Arab clans from supporting Deir az-Zour tribes against the SDF.

Meanwhile, five children were killed in Syrian regime shelling of a village near Manbij, Aleppo province, which SNA fighters seized overnight.

On Friday morning, local tribes launched a large-scale attack on SDF and Syrian regime military sites in Kurdish-controlled Manbij taking control of the Arab Hassan Ali hill and the village of Mahslani, where the children were killed.

Fighting has raged between the SDF and Arab tribes in Deir az-Zour since Monday, when the SDF detained the commander and several members of the Deir az-Zour Military Council (DMC) - a group affiliated with the US-backed group - during a meeting in the city of Hassaka.

The clashes pitted SDF members against the militia and some regional Arab tribesmen who have sided with the DMC killing 45 people including five civilians, according to the UK-based Syrian Observatory for Human Rights.

Mohsenli was struck by Russian warplanes as SDF and regime forces clashed with the tribal groups.

In Deir az-Zour, clashes between the DMC and the SDF saw casualties on both sides, as well as civilian deaths.

Wisam al-Akidi, an activist from Deir az-Zour, told al-Araby al-Jadeed that two civilians were killed on midnight on Thursday when an SDF drone struck a home in the town of Jadid Bakara.

Ten SDF fighters were captured in clashes with the DMC, while another 40 are reported to have defected after refusing to fight against the Arab clans.

The ongoing war in Syria began in 2011 to overthrow Bashar Al-Assad's regime and has led to hundreds of thousands of deaths.

Various factions have fought in the conflict, from the regime and its Iranian and Russian allies to Kurdish-led forces backed by the US.

On Thursday, the US military urged an end to the intra-faction fighting, warning that the clashes could pave the way for the return of the Islamic State group.