Eritrea's government has dismissed as a "vile slander" a UN report accusing it of human rights violations on a scale "seldom witnessed elsewhere".
The report was part of a campaign to undermine a nation which valued human rights, it said.
The UN published the report after a year-long investigation.
It said the government may have committed crimes against humanity, including a shoot-to-kill policy on its borders.
President Isaias Afewerki has governed the East African nation for 22 years, and the country has never held elections since gaining independence from Ethiopia in 1993.
Eritreans account for the second-largest group of migrants crossing the Mediterranean, after Syrians, with an estimated 5,000 fleeing every month.
The report said Eritreans flee the hardship caused by systematic and widespread human rights abuses.
Eritrea's foreign ministry said in a statement that the UN's allegations were "totally unfounded and devoid of all merit".
"They are an attack, not so much on the government, but on a civilised society and people who cherish human values and dignity," it added.
Eritrea at a glance:
- Gained independence in 1993
- 6.3m population
- Opposition parties outlawed
- Conscription can last until the age of 40
- UN estimates 5,000 Eritreans leave each month
- Heavily dependent on earnings of the diaspora