A Swedish human rights activist arrested in China earlier this month for allegedly posing a threat to national security has returned home after his expulsion, he said on Tuesday.

"I'm back in Sweden now. I arrived this morning, after various delays but I'm in my hometown now with my parents," said Peter Dahlin of the Chinese Urgent Action Working Group.

"I'm happy to be back but three of my colleagues and close friends are still being held," he told Swedish Radio.

Dahlin, who suffers from Addison's disease, said China had released him for "medical and diplomatic reasons".

The 35-year-old disappeared on January 4 as he prepared to board a flight to Thailand.

He appears to have been caught up in a crackdown on human rights lawyers.

Dahlin's group has said it offered training to lawyers who have tried to use the tightly controlled judiciary to redress apparent government abuses.

Chinese state broadcaster CCTV last week aired footage of a dazed and harried-looking Dahlin apologising to China for his alleged actions, which officials said had "threatened state security".

The Chinese government confirmed on Tuesday it had expelled him from the country.

"We have deported him," Hua Chunying, a foreign ministry spokeswoman, told a regular press briefing.

Dahlin's Chinese girlfriend, who had also been held, "has been released and there are no charges against her," the activist said.

The Swede's detention came as China considers a new law to control the activities of foreign non-governmental organisations, which has raised widespread concern among rights groups.

The ruling Communist Party has in recent months stepped up its scrutiny of NGOs, while state media has warned of "hostile foreign forces" said to be using them to foment revolution.

Authorities also launched a sweeping crackdown on human rights attorneys in July, detaining more than 130 legal staff across the country. This month at least 10 were formally arrested on charges related to "state subversion" after being held in secret for six months.

- 'Intimidation and fear' -

Observers said Dahlin's case was intended to send a warning to NGOs.

"I can see why the PRC released him now," Jerome Cohen, a law professor at New York University, wrote in a blog post, using shorthand for the country's official name, the People's Republic of China.

"The authorities made their point, spreading intimidation and fear throughout both the domestic and foreign legal and NGO worlds."

Rights groups echoed these sentiments, with Nicholas Bequelin, Amnesty International's East Asia director, writing on Twitter: "China has sent the clearest signal yet that it intends to cut domestic NGOs from foreign funding."

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

Gui, who was born in China, confessed to a drink-driving offence on the mainland dating back years and said he did not want Stockholm to interfere with his case.

He was rumoured to be among those preparing a tell-all book about the love life of President Xi Jinping.

Beijing only rarely accuses foreigners of endangering state security, a crime which can involve a heavy sentence.

But as Beijing has tightened social controls in recent years, it has sought to blame "foreign forces" for domestic woes, ranging from undermining Chinese values to a recent explosion in labour protests.

Swedish Foreign Minister Margot Wallstrom, who had protested to China about the detention of the two Swedish nationals, welcomed Dahlin's release.

"This is the result of close contacts between the Swedish foreign ministry and Chinese representatives," she said in a statement on Monday.

British MPs speak out over missing Hong Kong booksellers
Hong Kong (AFP) Jan 26, 2016 - Two British lawmakers Tuesday spoke out over five missing Hong Kong booksellers feared to have been detained in mainland China, calling for the case to be resolved quickly.

The disappearance of the five, from Hong Kong's Mighty Current publishing house known for salacious titles critical of Beijing leaders, has fuelled concerns freedoms in the semi-autonomous Chinese city are being eroded.

On a visit to Hong Kong's legislature, the British members of parliament insisted the UK had a legitimate interest in the case.

One of the five missing men, Lee Bo, 65, is a British citizen.

"The ambiguity around this case isn't helpful to China as much as it is to Hong Kong and the sooner that is resolved I think the better it will be for everybody," MP Jonathan Reynolds told reporters.

Reynolds and fellow MP Graham Brady are from the All Party Parliamentary China Group which deals with Bejing-London affairs.

"We're talking about a British citizen as well as talking about the rights and freedoms of Hong Kong so the British government has a proper and legitimate interest and has rightly expressed their concern," Brady said.

"We would hope, as I'm sure everybody here does, that this case be resolved as quickly as possible," Brady added.

The MPs met Hong Kong's deputy leader Carrie Lam as part of their visit.

Both the US State Department and European Union have expressed concern over the disappearances.

Bo, the last to vanish, was last seen in Hong Kong on December 30, sparking multiple protests in the city. Three other employees of the publisher went missing in southern China, and one in Thailand.

Letters purportedly sent by Lee to his wife claimed that he was safe and was "assisting in an investigation".

Another of the detained booksellers, Gui Minhai, who has Swedish nationality, was paraded on Chinese national television last week, saying he was in China to "take legal responsibilities" for killing a college student in a car accident there 11 years ago.

Gui, a Swedish national and co-owner of Mighty Current, reportedly failed to return from a holiday in Thailand in October.

Pro-democracy lawmakers, activists and some residents believe Lee was kidnapped in Hong Kong by mainland authorities. They accuse China of trampling on the "one country, two systems" agreement under which Hong Kong has been governed since its return by Britain in 1997.

Chinese law enforcers have no right to operate in the city.