BEIJING (Reuters) - Chinese authorities have detained a Swedish national who worked on legal aid and rule of law issues, on suspicion of endangering state security, a person with direct knowledge of the matter said on Tuesday.

Peter Dahlin was taken into custody on Jan. 4, the source said, amid a wider crackdown on rights activists in the country.

He is with the Chinese Urgent Action Working Group, whose website says it is made up of lawyers, academics and political professionals working with “a wide network of activists and leaders to assist fellow human rights defenders in distress.”

The Swedish Foreign Ministry confirmed the man, who is 35, had been detained. The Swedish embassy in Beijing said it has been in touch with Chinese authorities about meeting the detained man, said a spokesman who gave no further details.

Hong Lei, a spokesman for China’s Foreign Ministry, said he did not know about the detention.

Chinese President Xi Jinping has strengthened a crackdown on rights lawyers and foreign groups working on legal reform. Rights groups say the crackdown on their work aims to rein in dissent, a charge the Chinese government denies.

China has detained or formally jailed several foreign nationals in recent years, sometimes over their proximity to what it perceives as sensitive information.

At least two Japanese citizens were arrested on suspicion of espionage last year and a Canadian couple was arrested in 2014 amid a crackdown on foreign Christian groups along the country’s sensitive border with North Korea.