The arrests were made after a school director who defied government orders died in custody, says Sheila B Keetharuth, UN's human rights official in Eritrea.
Eritrean authorities detained hundreds of perceived opponents this month after a school director who defied government orders died in custody, the United Nations said on Wednesday.
Most of those arrested were males and some were as young as 13, Sheila B Keetharuth, the UN's Special Rapporteur for human rights in Eritrea told a UN Human Rights Council meeting in Geneva.
President Isaias Afwerki has led Eritrea since independence from Ethiopia in 1991 and his government operates a policy of compulsory military service that thousands each month flee the country to escape, according the UN.
There was no immediate comment from the government on Wednesday.
In 2016, the government rejected the allegations and said they were an attempt to harass the country.
Death of school official
This month's arrests followed the death in custody of Haji Musa Mohamednur, 93, who was a director of a private Islamic school in the capital Asmara and a respected elder, according to a UN statement.
He and other members of the school's administration were arrested last October for defying government orders including enforcing a ban on the veil and stopping religious teachings.
"Reports reaching me ... point to the arrest of hundreds of people, mainly males, some of them children as young as 13 years, after the burial of Haji Musa," the statement quoted Keetharuth as saying.
The statement gave no details of the circumstances of Musa's death this month.
'Indiscriminate mass arrests'
In October, there was a similar wave of detentions when law enforcement officers violently broke up a crowd and arrested over 100 people including students, she said.
"The indiscriminate mass arrests in October 2017 and during the past week were carried out to quell any kind of protest or resistance," she said.