The United Nations on Friday slammed Thailand's deportation of two Chinese refugees, and Vietnam's reported transfer of nine North Korean nationals to China, warning they were at risk of "grave human rights violations"

Ravina Shamdasani, spokeswoman for the UN human rights agency, told reporters that Thai authorities had, for unknown reasons, deported two recognised Chinese refugees who had been due for resettlement in a third country.

"We have expressed our concern to the government of Thailand about their deportation," she said, pointing out that the move came just months after the country was criticised for deporting 109 ethnic Uighurs to China.

"The principle of non-refoulement, which prohibits the return of a refugee to a country where he or she is likely to face persecution or torture, is contained in Article 3 of the Convention against Torture and other Cruel, Inhumane or Degrading Treatment or Punishment to which Thailand is a party," she stressed.

Pointing to allegations that torture remains widespread in police custody in China, Shamdasani urged the Thai government "to stop deporting individuals, including potential refugees and asylum seekers, to countries where there are substantial grounds to believe that they would face an imminent risk of grave human rights violations, including torture."

Shamdasani also voiced alarm over reports that Vietnam had last month arrested nine North Korean nationals, including a one-year-old and a teenager, and transferred them to China -- North Korea's main ally.

"There are fears that they may be, or may already have been, repatriated to the Democratic People's Republic of Korea, where they would be at risk of very serious human rights violations," she warned.

Her comments came a day after a UN General Assembly committee condemned "long-standing and ongoing systematic, widespread and gross violations of human rights" in North Korea.

Shamdasani said the UN agency had received information indicating the North Koreans, along with a child who has a North Korean mother and a Chinese father, had been arrested in Vietnam on October 22, and later sent to the Chinese town of Dongxing near the Vietnamese border.

The were reportedly moved to Shenyang, near the North Korean border, on November 17, after which the group of nine was taken out of the city, while the dual national child was left behind.

"It is believed that the group is being escorted by the Chinese authorities," Shamdasani said, adding that "the current whereabouts of the nine individuals are unknown."

"This series of events strongly suggests that the group is at imminent risk of being repatriated to the DPRK, and we are gravely concerned that they may already have been returned," she said, calling on Vietnam and China to clarify their fate.

"We further urge all concerned governments to refrain from forcibly returning individuals who have fled the DPRK," she said.