A Swedish activist detained in China was accused by state media Tuesday of inciting government opposition and was said to have "apologised", the latest in a deepening crackdown on human rights lawyers.

Peter Dahlin, who worked for the Chinese Urgent Action Working Group, was detained earlier this month as he prepared to board a flight from Beijing.

It is rare for China to accuse foreigners of national security offences, which can carry heavy penalties, although some have been accused of spying.

The official Xinhua news agency said Dahlin's group, also known as China Action, was "encouraging the masses to oppose the government".

It did not clearly state which of his activities constituted a crime, only that China Action staff "collected many kinds of negative information about China, and distorted them... to provide so-called China human rights reports".

China Action has said it offered training to human rights lawyers who have tried to use China's tightly-controlled judiciary to redress apparent government abuses.

Authorities launched a sweeping crackdown against human rights attorneys in July, detaining more than 130 legal staff across the country.

This month at least 10 were formally arrested on "state subversion" related charges after being held in secret for six months.

Xinhua said China Action had worked closely with the Beijing-based Fengrui Law Firm, at the centre of the July crackdown, providing its lawyers with funding.

The news agency quoted Dahlin as saying, apparently while detained: "In China I committed illegal acts, and hurt the Chinese government and people. For this I deeply apologise".

"Our reports were gathered from online information... and we can't ensure that all the information is accurate", it also cited him as saying.

China regularly publishes "confessions" from alleged criminals in state media. Lawyers say such statements are often made under duress and violate the right to a fair trial.

- 'Smear attempt' -

Xinhua also said a detained colleague of Dalhin, surnamed Wang, helped him to kick up anti-government dissent.

"The things I helped Peter do, objectively, were serving anti-Chinese forces to attack China, providing them with ammunition, causing serious danger," Xinhua reported.

"I am keenly willing to admit guilt and express regret."

It cited Wang as saying Dahlin and his colleagues were "informants for Western anti-Chinese forces planted in China, collecting all kinds of negative information used by foreign forces to blacken the international image of China".

Michael Caster, a US-based spokesman for China Action, condemned the Xinhua report as "an attempt to smear someone engaged in efforts to support the development of the rule of law in China".

Sweden summoned China's ambassador after Dahlin's detention, which has raised fears about the ruling Communist Party's lack of respect for legal procedure, even foreigners, as it cracks down on critics.

China denied Dahlin access to consular officials for weeks after his detention, China Action said, adding that his girlfriend -- a Chinese national -- had also been held.

Chinese state-run media often accuse foreign aid organisations of undermining national security and trying to provoke a "colour revolution" against the Communist Party.