Four Chinese students who recently traveled to the United States to study and participate in academic conferences suffered unwarranted harassment, interrogation and repatriation by the US side, sources said.

The four students have scientific and technical backgrounds, and two of them have research interests in artificial intelligence, the sources familiar with the matter told China Daily on the condition of anonymity.

US Customs and Border Protection officers took the four Chinese individuals to a darkened room for more than 10 hours of continuous interrogation, repeatedly questioning them with a baiting, coercive approach, the sources said.

The officers repeatedly questioned them about their personal and family information, their studies and internships in the US, whether they were members of the Communist Party of China, and whether they had cooperated with the Chinese government.

The officers "paid particular attention to political backgrounds such as CPC membership, and to scientific research backgrounds related to computers", one of the sources said.

The US side also refused to allow two of the individuals to contact their families and friends, causing one of them to be out of contact with the outside world for more than 30 hours, the source said.

In addition, without evidence or valid warrants, the US side arbitrarily seized the electronic products of one of the Chinese individuals and repatriated the other three students. How the fourth student's case was resolved was not disclosed.

The US side in recent years has conducted unwarranted harassment, interrogation and repatriation of more than 30 Chinese students majoring in computer-related fields, according to incomplete statistics.

The vast majority of them are master's or doctoral degree candidates, with more than half of them being PhD candidates, and most of them are studying in well-known universities in the US.

Their research interests cover fields such as artificial intelligence, information science, network security, electronics, software engineering and electronic information engineering.

"Mostly, these students were harassed and interrogated by the US side for more than 10 hours upon entering the country, and the longest time of being held was even up to five days, and ultimately, without exception, their visas were canceled and they were repatriated," another source said.

The US practice is "far beyond the realm of normal law enforcement, is strongly ideologically biased, and is not aimed at maintaining so-called 'national border security'," the source said, adding that the aim is to hold back China's scientific and technological development and maintain US scientific and technological hegemony, which "fully reflects the hegemonic, bullying nature of the US side, as well as its anxiety and lack of self-confidence in the realm of science and technology".

Such practices will only give rise to a serious "chilling effect" inside and outside the US, poison the public opinion environment for China-US relations, and impede the mutual visits and exchange of talent between the two countries, the sources said.

The US will eventually damage its own international image and innovation vitality, leading to a serious backfire, a third source said.

"Chinese students should assess the risk with great caution and think twice before going to the US to study," the source added.

Su Xiaohui, deputy director of the Department of American Studies at the China Institute of International Studies, said that Washington is sparing no effort to fan competition among major countries and secure its hegemony, and such harassment aims to disrupt and frustrate regular exchanges between the two countries on education, science and technology.

Behind such harassment is the fact that some anti-China forces in the US have constantly hyped the so-called "China threat", and this kind of harassment "serves to build on their anti-China narrative and China-threat narrative", Su said.

"Fundamentally, this is an issue of perception," she said. "When Washington views China as a rival and a threat, it seeks to undermine China in a relentless way."