A Swedish man working for a human rights group in China has been detained on suspicion of endangering state security, his colleague said Tuesday, as Beijing steps up controls on civil society.

Peter Dahlin, who worked for the Chinese Urgent Action Working Group, was detained earlier this month as he prepared to board a flight in Beijing, colleague Michael Caster told AFP.

A spokeswoman for US-based charity Chinese Human Rights Defenders earlier said he was detained at the city's airport on January 4.

It identified him by a different name.

The Group says online that it seeks to aid "human rights defenders in distress".

A document apparently submitted by the group to the UN detailed "intimidation, surveillance, and house arrest to physical attacks, enforced disappearance and arbitrary detention" of activists.

A Beijing telephone number listed on the document went unanswered on Tuesday. China's foreign ministry said it was unaware of the case.

Sweden's embassy in Beijing said in an email that "a Swedish citizen, man in his mid-thirties, has been detained in China", adding: "The Embassy is investigating this."

China's ruling Communist Party under President Xi Jinping has stepped up a campaign against outspoken academics, lawyers and human rights activists, which has seen hundreds detained and dozens jailed.

It has also drafted a new law that would put overseas non-governmental organisations (NGOs) under close supervision by Chinese police while operating in the country.

Chinese state-run media often accuse foreign NGOs of undermining national security and trying to foment "colour revolution" against the Communist Party.

According to drafts of the law being considered by the Communist-controlled legislature, overseas NGOs will have to "partner" with at least one Chinese government department.

They will also have to submit "work plans" detailing their activities to Chinese police for approval, among other measures.

Overseas charities and business groups have said they believe the law will seriously restrict their operations in China, and the vague wording of its references to "security" has raised fears it could give police wide-ranging discretionary powers over NGOs.