GENEVA - The U.N. human rights chief Volker Turk on Friday called for an immediate moratorium on the use of the death penalty in Iran, warning that dozens more people risk execution after the first death sentence linked to January mass protests was issued this week.

"I am horrified by reports that at least eight people, including two children, have been sentenced to death in connection with the protests," Turk said in a speech to the U.N. Human Rights Council in Geneva, adding that another 30 people appeared to be at risk of the same sentence.

A revolutionary court in Tehran issued a death sentence for an Iranian man accused of "enmity against god" which if confirmed would be the first such sentence linked to mass protests in January, a source close to the man's family said.

Rights groups say thousands of people were killed in a crackdown on the protests, the worst domestic unrest in Iran since the era of its 1979 Islamic Revolution. During the unrest, U.S. President Donald Trump warned Tehran that he could order military action if it carried out executions.

"I am extremely alarmed about the potential for regional military escalation and its impact on civilians, and I hope the voice of reason prevails," Turk said in the same speech.

Talks in Geneva on Thursday between the United States and Iran made progress over Tehran's nuclear programme, mediator Oman said, but there was no sign of a breakthrough that could avert potential U.S. strikes amid a massive military buildup.

-Reporting by Emma Farge, Editing by Friederike Heine, Kirsti Knolle/Reuters