SEOUL: A group of 11 North Koreans who were detained in Vietnam while seeking to defect to South Korea have been released thanks to the help of European institutions, a Seoul-based activist group said on Saturday.

The eight women and three men were caught by border guards in northern Vietnam in late November after crossing from China, and had been held in the northeastern border city of Lang Son.

Peter Jung, who heads the group helping the refugees, Justice for North Korea, said they were freed and on their way to South Korea last month.

Multiple European organisations played a key role, he said. He declined to identify them due to the diplomatic sensitivity but said they included a non-government group.

The Wall Street Journal reported on Friday that US officials, including diplomats engaged in denuclearisation talks with North Korea, intervened to secure the defectors' release, citing unidentified sources.

But Jung said he was unaware of any US contribution.

South Korea's foreign ministry said the government made immediate efforts to prevent the defectors from being forcibly repatriated, but refused to elaborate.

"The European institutions acted after we published a video of the refugees making desperate appeals for freedom," Jung said. "The South's foreign ministry got also involved later."

Jung had distributed a video of some of the 11 protesting against deportation before appearing to faint.

About 33,000 North Koreans have resettled in the affluent, democratic South. Most risked their lives to cross the border in a journey that may entail persecution and slave labour, if caught and repatriated.

As living examples of some of Pyongyang's worst abuses, defectors have long been the public face of campaigns to pressure Pyongyang to change its ways.

But South Korean President Moon Jae-in has been criticised by groups like Jung's for not helping defectors enough and ignoring human rights issues as promotes rapprochement with the North.

In November, after brief questioning, South Korea expelled two North Korean fishermen calling them criminals who murdered 16 colleagues before crossing the border into the South.

A coalition of defector groups issued a joint statement criticising the decision, saying the men should have been tried in the South because they would likely face torture, and possibly execution back home.