Syrian authorities have arrested state security personnel who committed "violations" in July in a region largely inhabited by the minority Druze sect during some of the worst violence in the country since the fall of the Assad regime.

The head of a government committee investigating the fighting in Sweida province said videos on social media showing "transgressions" were used as the basis for detaining an unspecified number of people.

"The faces were clear [in the videos]. They were referred to the judiciary," said Hatem Naasan, the judge who heads the National Commission for Investigation of the Sweida Events. Formed in August, the committee "has not been subject to any pressures from the Syrian state", he added.

Under a US-brokered deal in September to reconcile the Syrian government with the Druze, authorities in Damascus committed to prosecuting those involved in violence against civilians during an attack by state forces aimed at subduing Sheikh Hikmat Al Hijri, a spiritual leader of the sect who opposes Syria's central government.

Mr Naasan said the committee's investigators had not been allowed into Druze-populated areas of Sweida controlled by a de facto Druze administration loyal to Mr Al Hijri, but had contacted many Syrians inside.

However, the UN's Independent International Commission of Inquiry on Syria has been working in Sweida since last month after Mr Al Hijri allowed in some of its members.

Syrian government security forces gather on a hillside in Busra Al Harir, near Sweida province. AP

Rayyan Maarouf, a researcher at Suwayda24, a network of citizen journalists, said the committee lacks credibility because it has no access to the "scene of the crimes" in Sweida. Many in the area, he said, regard it as a tool of the central government.

"It has shown no interest in investigating the chain of command that allowed the massacres," Mr Maarouf told The National from Sweida city, the provincial capital. "The killings were not traffic accidents."

He said body counts verified by Suwayda24 showed 1,510 Druze were killed in the government offensive. Among them were 50 children and 115 women, he added. Sixty-six civilian members of Bedouin tribes were killed in revenge attacks, including women and children.

Druze residents of Sweida expressed scepticism about the government's investigation into the attacks, which further alienated the community from the authorities in Damascus.

Mounir Mansour Al Chaar, a dentist, said he submitted his testimony, along with dozens of videos he filmed, to the UN commission in October. He said he did not trust the national committee and would refuse to talk to its investigators should they ask.

“A person cannot be both judge and executioner,” he said.