The United Nations expressed alarm on Friday about the fate of nine North Koreans feared to have been deported from Vietnam via China back to their homeland, saying they might face torture or even execution. Forcibly sending refugees back to a country where they could suffer persecution, a practice known as “refoulement,” is banned under international treaties signed by China. “We are alarmed at reports that nine North Korean nationals, including a 1-year-old infant and a teenager, were arrested in Vietnam last month and subsequently transferred to China,” Ravina Shamdasani, a United Nations human rights spokeswoman, said at a briefing in Geneva. “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.” The North Koreans were arrested in Vietnam on Oct. 22 and were thought to have been sent to the Chinese city of Shenyang, close to the North Korean border. In recent years many North Koreans have fled their country into China, traveled on to Southeast Asia and then to South Korea or other countries. The Chinese authorities are believed to have been escorting the nine North Koreans, Ms. Shamdasani said. “We urge the Chinese and Vietnamese authorities to publicly clarify the fate of the nine North Korean nationals,” she said.