The UN temporarily shut its European headquarters on Friday due to a “security issue”.
It later announced the building in Geneva, Switzerland, had reopened without providing further details.
"Please be informed that the issue at the Palais des Nations has now been solved. All the access points have been reopened," it said.
The organisation said earlier that an issue was being “actively investigated by the UN security and should be resolved soon”.
The Palais des Nations building houses the Human Rights Council and is a centre for diplomats, humanitarian workers and state officials.