Photos posted on the social media platform X suggested the trip was mostly attended by close Chinese allies.
U.N. experts have this year voiced repeated concerns over Tibet, which is administered by Beijing as an autonomous region within China, most recently in August when they raised the plight of jailed Tibetan rights defenders.
The United States last week imposed visa sanctions on unnamed Chinese officials for allegedly taking part in "forced assimilation" of Tibetan children through state-run boarding schools seeking to eliminate Tibet's traditions, according to a statement from U.S. Secretary of State Antony Blinken.
China's foreign ministry on Thursday vowed "reciprocal" measures and condemned U.S. "lies on Tibet".
China has also faced criticism for its treatment of Muslims in its Xinjiang region, which the U.N. said a year ago may constitute crimes against humanity.
China vigorously denies any wrongdoing in Tibet or Xinjiang.
U.N. member states are set to publicly examine its rights record in early 2024 as part of a review process at the Human Rights Council in Geneva.
A letter sent by China's ambassador to the U.N. in Geneva seen by Reuters invited diplomats to Beijing and the "XiZang Autonomous Region", using China's term for Tibet.
"I trust this trip will allow you to better understand China's human rights policies and practices," Chen Xu said, mentioning meetings and field visits on education, culture, religion, employment and children's rights.
China's diplomatic mission in Geneva did not immediately respond to a request for comment. Its foreign ministry said in a statement on Thursday that vice foreign minister, Ma Zhaoxu, met with a delegation of developing countries on human rights, without mentioning Tibet.
Reuters could not determine who was invited on the Tibet trip, although two diplomats said the invitation had been distributed widely. Photos posted on X by Cuba and China showed envoys from Cuba, Venezuela, Nicaragua, Belarus and Pakistan among the group.
Official trips to Tibet have been much rarer than to Xinjiang. This week, Xinjiang Communist Party Secretary Ma Xingrui met with a representative from the International Labour Organization, state media said, in what it said was a sign of the region's "open attitude".
The ILO confirmed in an email that it had conducted a mission and discussed China's implementation of labour conventions covering discrimination and forced labour.
(Reporting by Emma Farge in Geneva and Laurie Chen in Beijing; editing by John Stonestreet and Conor Humphries)
By Emma Farge and Laurie Chen