South Korea has asked U.N. human rights agencies to help ensure the safety of nine North Korean defectors who were repatriated to the North from China after being caught in Laos, a senior Seoul official said Thursday.

The North Koreans, aged between 15 and 23, fled their country to Laos via China last month. They were forced to return home on Tuesday, a day after they were deported to China from Laos after being rounded up by the Lao authorities on May 10.

South Korea had appealed to both Laos and China to send them to Seoul, but the plea was rejected.

"The government has asked U.N. human rights and refugee agencies to cooperate with the repatriation of the North Korean defectors," the official at Seoul's foreign ministry said.

Diplomatic sources in Seoul say at least one North Korean agent was on board the Air Koryo flight to Pyongyang with the defectors, indicating that the North Korean government was involved in the deportation.

Foreign Minister Yun Byung-se sent a special envoy, Ambassador Lee Jeong-kwan, to Laos and lodged a "strong protest" with the Lao government for deporting the North Koreans, the official said.

In return, Laos told the South Korean envoy that it decided to send the defectors to China in an effort to improve its tainted image of cross-border crimes such as illegal immigration and human trafficking, according to the official.

In the wake of this week's deportation, the official said that Laos may deal with the issue of North Korean defectors there "by its own rules."

Meanwhile, a local newspaper reported that the son of a Japanese women abducted by North Korea in the 1970s was among the nine North Koreans who were repatriated to the North this week.

However, the South Korean government did not have any information on that at the time of reporting, the official said.

Laos has become one of the major transit points for North Korean defectors, who flee their homeland through China with the aim of eventually entering South Korea.

Tens of thousands of North Korean defectors are believed to be hiding in China, hoping to travel to Laos, Thailand or other Southeast Asian countries before resettling in South Korea, which is presently home to more than 25,000 North Korean defectors.

North Korean defectors face harsh punishments and even execution after being repatriated from China, which does not recognize them as asylum seekers, according to defectors in South Korea and human rights activists. (Yonhap News)