China detains US nuclear expert over espionage allegations

China has detained a US-based seismologist who studied nuclear testing activities, with his family claiming that he has been held for nearly two years on espionage allegations they strongly reject.

Chen Youlin, a 54-year-old scientist and US citizen, was arrested in November 2024 while visiting relatives in Beijing, according to a hostage advocacy group. His family decided to publicly raise the issue after receiving no indication that Chinese authorities planned to release him.

Chen’s wife, Rong Yufang, who is also a seismologist, said the accusations against her husband were unfounded and did not match the nature of his scientific work. She said Chen’s research was conducted openly through international academic cooperation.

Chen specialised in analysing seismic data to identify and study nuclear tests. Much of his published research focused on monitoring North Korea’s nuclear activities, including underground tests conducted by Pyongyang.

It remains unclear whether Chen’s research had any connection to China’s own nuclear programme. Beijing has denied allegations of conducting secret nuclear tests, while US officials have previously raised concerns about China’s expanding nuclear capabilities.

China’s foreign ministry said authorities handle all cases according to the law and rejected claims of wrongful detention. Officials said there was no such thing as unlawful detention in the case.

Chen’s family says he has been denied normal legal access for an extended period. His wife said she has not spoken directly with him for more than 600 days and expressed concern about his health. She claimed Chinese authorities questioned him repeatedly about his research and that he was unable to meet a lawyer during the early months of detention.

Born in China, Chen became a US citizen in 2011 and later worked in Boston, Massachusetts. His research included projects supported by the US government and focused on improving methods to detect and analyse nuclear explosions using seismic information.

A US-based advocacy group said Chen’s arrest may be linked to wider tensions over nuclear monitoring and international security. The group suggested that his expertise could provide insight into US methods for detecting nuclear tests, though no evidence has been publicly presented to support the claim.

Chen’s supporters argue that his case could discourage scientific cooperation between researchers in China and the United States. US Senator Edward Markey also criticised the detention, saying it could damage academic and diplomatic relations between the two countries.

Human rights groups have raised concerns about Chen’s health, saying he requires regular medical care for existing conditions, including diabetes and high blood pressure.