STOCKHOLM (AFP) - A Swedish human rights activist held by China since early January for allegedly posing a threat to national security has been released, Sweden's foreign ministry said Monday.

"I welcome the fact that Peter Dahlin can now be reunited with his family in Sweden. This is the result of close contacts between the Swedish foreign ministry and Chinese representatives," Foreign Minister Margot Wallstrom said in a statement.

Dahlin, who worked for the Chinese Urgent Action Working Group, disappeared earlier this month as he prepared to board a flight to Thailand, and appears to have been caught up in a crackdown on human rights lawyers.

His detention came as China considers a new law to control the activities of foreign non-governmental organisations (NGOs), which has raised widespread concern among overseas groups. Dahlin's group has said it offered training to lawyers who have tried to use China's tightly-controlled judiciary to redress apparent government abuses.

State broadcaster CCTV last week aired footage of a dazed and harried looking Dahlin apologising to China for his alleged actions.

Another Swedish national, China-born Hong Kong bookseller Gui Minhai, disappeared from Thailand late last year before reappearing on Chinese national television in police custody.

He confessed to a years-old mainland drink-driving offence and said he did not want Stockholm to interfere with his case.

Wallstrom said she remained "greatly concerned" about Gui.

"Our efforts to get a clear picture of his situation and the possibility to visit him continue with undiminished force," she said.