"We are receiving extremely disturbing reports of entire families, including women, children and hors de combat fighters, being killed," said Volker Türk in a statement.

"There are reports of summary executions on a sectarian basis by unidentified perpetrators, by members of the caretaker authorities' security forces, as well as by elements associated with the former government."Groups terrorising civilians

He said the caretaker authorities' announcements of their intention to respect the law must be followed by swift actions to protect Syrians, including by taking all necessary measures to prevent any violations and abuses and achieve accountability when these occur.

"There must be prompt, transparent and impartial investigations into all the killings and other violations, and those responsible must be held to account, in line with international law norms and standards," he said. "Groups terrorising civilians must also be held accountable."

These events as well as the continuous spike in hate speech both online and offline illustrate once again the urgent need for a comprehensive transitional justice process that is nationally-owned, inclusive, and centred on truth, justice and accountability, he said.