Protests have gripped Iran since Mahsa Amini, a 22-year-old of Kurdish origin, died on September 16, three days after her arrest in Tehran by the notorious morality police for allegedly breaching the Islamic dress code for women.

"Iran is in turmoil in part as a consequence of the killing" of Amini, Javaid Rehman told a press conference, describing her as "a victim of state brutality and state repression."

"Protesters are seeking justice," he said.

Underscoring an "absence of any domestic channels of accountability," Rehman called for the international community to set up an international investigative mechanism aimed at ensuring that Iran answers "for what has happened since the death of Jina Mahsa Amini."

"Clearly there has been a lot of brutality," he said, adding that "a minimum of 250 people who have been killed by the state since the wave of these protests started" in mid-September, including more than 25 children.

He said, however, that the figure was "very conservative" and that there was "no doubt" many more people had been killed.

He also slammed the "problematic" role of the morality police, saying they "used violence in (Amini's) case" and in many other cases, underscoring "very serious systemic problems."

Six weeks since Amini's death, protests have continued across Iran, despite a crackdown that has seen scores of protesters also injured and arrested.