Iran has executed at least 21 people since the start of the conflict with the ‌United States and Israel two months ago and has arrested more than 4,000 on national security-related charges, U.N. human rights chief Volker Turk said Wednesday.

Turk said at least nine people have been executed in connection with protests in January, 10 for alleged membership in opposition groups, and two ‌on espionage charges.

"I am appalled that – on top of the already ​severe impacts of the conflict – the rights of the Iranian people continue to be stripped from them by the authorities, in harsh and ⁠brutal ways," Turk said in a statement.

"I call on the authorities to halt all ​further executions, establish a moratorium on the use of capital punishment, fully ensure due process ⁠and fair trial guarantees, and immediately release those arbitrarily detained," he said.

Iranian authorities killed thousands of people during anti-government protests in January, Iran's worst domestic unrest since the era of its 1979 Islamic Revolution. Rights groups ‌said the government has continued to crack down on opponents during the conflict.

Iran ​in January rejected ‌condemnation by the U.N. Human Rights Council as "politicized."

Last week, Norway-based Iran Human Rights said that at least 3,646 people have ‌been arrested, with at least 767 cases reported following the start of a ceasefire on April 8.

Turk said that many of the thousands detained "have been forcibly disappeared, tortured, ⁠or subjected to other forms of cruel, ‌inhuman and degrading treatment, including ⁠coerced – and sometimes televised – confessions and mock executions."

He said individuals from ethnic and religious minorities had been at ⁠particular ⁠risk.

"Dozens of prisoners have been transferred to unknown locations with no information on their fate, among them human rights lawyer Nasrin ‌Sotoudeh," he said.

Turk said the health of Nobel Peace Prize laureate Narges Mohammadi was reportedly worsening after she suffered a heart attack, and her medical condition was compounded by existing chronic ‌medical conditions ​resulting from her arrest.

Turk said ‌that in Chabahar Prison, which is in southeast Iran, security forces reportedly killed at least five people and injured 21 after confronting people protesting a ​prolonged suspension of food distribution. He said two more detainees died in custody in a different prison, with indications that they had been subjected to torture.