The United Nations Tuesday opened a new office in Seoul to monitor North Korea's human rights record, after accusing the isolated regime of abuses "without parallel in the contemporary world" in a report published last year.
The office was formally opened in a ceremony attended by UN High Commissioner for Human Rights Zeid Ra'ad Al Hussein, despite Pyongyang repeatedly threatening "merciless punishment" against South Korea if the mission was launched.
South Korea urged the North to stop criticising the new UN office after it suddenly announced it would boycott next month's World University Games, also known as the Universade, in the southern city of Gwangju.
In a message emailed to the Gwangju Universiade organising committee last week, a North Korean sports official said the UN office in Seoul drove inter-Korean relations to "the extreme situation" and "cooled down our atmosphere to participate in the games".
"Less than 50 miles from here lies another world marked by the utmost deprivation," Hussein said in a statement to mark the opening.
"The Seoul office will monitor and document human rights issues in (North Korea), building on the landmark work of the commission of inquiry and special rapporteur. We firmly believe this will help the basis for future accountability," he said.
Many North Koreans have escaped to find a new life in the South, but millions remain "trapped in the grip of a totalitarian system which not only denies their freedom but increasingly their basic survival needs", he added.
Human Rights Watch's deputy Asia director Phil Robertson described the new UN office as a "critical step forward" in the campaign to end North Korea's "systematic and pervasive human rights abuses".
About 20 activists rallied in Seoul against the opening of the mission, saying it would be used to "bring down" the North Korean government and would aggravate strained inter-Korean relations.
The United Nations proposed opening the field office following a searing report by a UN commission published in 2014 that concluded North Korea was committing human rights violations "without parallel in the contemporary world".
Based on the testimony of hundreds of North Korean exiles, the commission detailed a vast network of prison camps holding up to 120,000 people and documented cases of torture, summary executions and rape.
The report formed the basis of a resolution adopted by the UN General Assembly urging the Security Council to consider referring Pyongyang to the International Criminal Court. Pyongyang has categorically rejected the findings of the UN commission, labelling it a work of fiction authored by the United States and its allies.
Cross-border tensions have remained high this year due to a series of North Korean ballistic missile tests, nuclear threats and annual US-South Korean military exercises.
Pyongyang sees the joint drills, most recently carried out in March and April, as a rehearsal for invasion.