SEOUL--Eleven North Koreans wanting to defect to South Korea have been detained in Vietnam since Nov. 23 and are seeking help to avoid being repatriated, a South Korean activist group said on Monday.

The eight women and three men were detained by border guards in northern Vietnam two days after crossing from China and are being held in the city of Lang Son, the Seoul-based Justice for North Korea said in a statement.

Peter Jung, the head of the group, which supports North Korean asylum-seekers, said the would-be defectors had requested help from the South Korean Embassy in Hanoi, but he had not heard from them since Friday.

Jung said the Seoul embassy's subsequent silence had spurred him to publicize the situation, fearing that without an international response the defectors could be forcibly repatriated.

He said that on Thursday Vietnamese authorities called off an effort to deport the defectors after several of them protested passionately and appeared to faint.

Vietnam's foreign ministry did not immediately respond to a request for comment.

The South Korean Foreign Ministry said it was aware of the case and had been in touch with the Vietnamese government to try to prevent the defectors from being sent back to North Korea.

"Our government has been making necessary efforts to ensure the North Korean defectors living abroad are sent to a desired place without being forcibly repatriated," the ministry said in a statement.

South Korean President Moon Jae-in has been trying to make diplomatic progress with North Korea, and his government has been criticized by groups like Jung's for not doing enough to help defectors in recent months.

Last month South Korea expelled two North Korean fishermen suspected of killing 16 colleagues before crossing the border into the South, after detaining them for questioning.

That decision drew criticism and dismay from some defectors, who said the men should have been tried in the South and would likely face torture, and possibly execution, in North Korea.

As of September, at least 771 North Korean defectors had entered South Korea this year, according to the South's Unification Ministry, which handles relations with the North.

Around 33,000 North Korean defectors live in South Korea.