Iranian authorities have arrested Farideh Moradkhani, a niece of Supreme Leader Ayatollah Ali Khamenei, according to her brother and human rights activists.

Mahmoud Moradkhani wrote on Twitter that his sister had been arrested on Wednesday as she was summoned by the prosecutor's office in Tehran.

Farideh Moradkhani is an engineer and a well-known rights activist. She has been a vocal critic of the government's crackdown on anti-government protests. 

Iran has seen weeks of unrest since the death of the young Kurdish woman Jina Mahsa Amini in police custody. 

According to Norway-based NGO Iran Human Rights, at least 416 people, including 51 children, have been killed in Iran's crackdown on the protests that followed Amini's death in September.

What we know about the arrest

Farideh Moradkhani was arrested earlier this year by Iran's Intelligence Ministry and released on bail.

Activist news agency HRANA said Moradkhani was now being held in Tehran's Evin security prison.

According to HRANA, her arrest last Wednesday was to begin serving an existing 15-year sentence. The charges were not immediately clear.

Mahmoud Moradkhani later posted a video on social media in which his sister called Iran's clerical leadership a "murderous and child-killing regime."

What did Moradkhani say in the video?

"O free people, be with us and tell your governments to stop supporting this murderous and child-killing regime," Moradkhani said in the video.

"This regime is not loyal to any of its religious principles and does not know any rules except force and maintaining power," Moradkhani added.

Moradkhani called on "all free and democratic countries to recall their representatives from Iran as a symbolic gesture and to expel the representatives of this brutal regime from their countries."

She said sanctions imposed on Tehran were "laughable" and that Iranians had been left "alone" by the world.

Moradkhani is the daughter of the late Ali Moradkhani Arangeh, a prominent opposition figure and Shiite cleric who married Khamenei's sister.

Khamenei's sister, Badri, fell out with her family in the 1980s and fled to Iraq during the Iran-Iraq war. 

sdi/fb (AFP, Reuters)