The body is debating a motion brought by a group of some 50 countries led by Germany and Iceland to create a new investigative fact-finding mission to probe alleged abuses since a wave of protests began over the death in custody of 22-year-old Kurdish woman Mahsa Amini on Sept. 16.
The meeting is seen as a key test of the West's clout within the council following a thwarted attempt to create greater scrutiny of China's human rights record last month.
"We are now in a full-fledged human rights crisis," High Commissioner of Human Rights Volker Turk said in his first address to the council since starting last month.
"The unnecessary and disproportionate use of force must come to an end," he said. Turk added that so far, more than 300 people have been killed in the protests, including more than 40 children, while around 14,000 have been arrested.
Tehran's representative called the debate disgraceful and appalling.
Iran has been lobbying against the motion and sent a delegation to Geneva earlier this month to urge countries to vote against the resolution as well as sent diplomatic missions a series of documents seen by Reuters.
(Reporting by Emma Farge; Editing by Maria Sheahan and Miranda Murray)

Khadijeh Karimi, deputy of the vice president for women and family affairs of the Islamic Republic of Iran, speaks during a Human Rights Council's special session on the deteriorating human rights situation in Iran, at the European UN headquarters in Geneva, Switzerland, November 24, 2022. EPA-EFE/MARTIAL TREZZINI SWITZERLAND OUT