Authorities in Afghanistan's western city of Herat arrested at least 30 women, accusing them of violating dress rules imposed by the Taliban government, the UN said in a statement, adding that some were later released.
Thursday's statement followed a clampdown on protests against the arrests in Herat's district of Injil on Tuesday.
"The arrests have heightened fear and apprehension among women and girls across Afghanistan," the statement said, quoting UN Women, an agency advocating for women's rights.
In a separate statement, the UN Assistance Mission in Afghanistan said it was alarmed by what it described as excessive use of force against protesters in Herat.
"According to the independent experts, Taliban security forces allegedly opened fire on protesters - men, women and children - administering beatings to some," Thursday's UN statement said.
"At least two people, including a boy, were killed and more than 20 were injured."
Media said officials from the Taliban's morality police, the Department for the Promotion of Virtue and Prevention of Vice, had detained some women in the days before the protests for allegedly failing to comply with hijab regulations.
Local authorities have denied reports that women were arrested.
Since seizing power in Kabul in 2021, the Taliban have imposed sweeping restrictions on women and girls in the war-shattered country, including limits on access to education, employment and sport, drawing international criticism.

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