China's foreign ministry has criticized what it says is the discriminatory treatment of Chinese students trying to enter the United States after reports of prolonged interrogations and coercion, with some seeing their visas revoked upon arrival in the U.S.

At least seven Chinese students, all women, who flew to the Washington DC area recently to further their studies in the U.S. were deported without explicit reasons, according to a report by China Science Daily, a media outlet administered by the Chinese Academy of Sciences.

One of the Chinese students recalled her experience to the newspaper. She was unwilling to provide her name for fear of repercussions.

The doctoral candidate took off from Beijing and landed at Washington Dulles International Airport on Dec 19. Her nightmare began when she was directly stopped by U.S. Customs at the airport for further inspection in a secondary checking room, commonly known as the "little black room" among Chinese students. It took eight hours.

Customs officers told her that her visa was "invalid" despite it being issued by the U.S. embassy in China, and she would be deported. Her only option was to pay $3,700 for the plane ticket, she said.

The student said that customs officer coerced to sign documents saying that she had entered the U.S. illegally and that she agreed with her own deportation. She claimed the customs officer said she would be able to return to the U.S. as long she flew home and reapplied for a visa, without mentioning the five-year ban she was about to face.

After being held for eight hours in what she described as the "terrifying little black room", she said then endured another 12 hours confined to a room without any of her personal belongings and kept under surveillance. Her coat, shoes and sweater were removed, and she was not even allowed her cough medicine.

With just a little over an hour's sleep, she underwent her third body search and a further five hours in confinement while transferring at Los Angeles International Airport before finally boarding a flight back to Beijing.

If her appeal against the five-year ban isn't successful, she will fail to defend her doctoral degree dissertation in the U.S. this year. Even if she succeeds, the process will take at least six months, seriously holding up her biology experiments, she said.

At least six other female students have been deported at the Dulles Airport in recent months, and they've connected through social media to share their similar experiences, according to the China Science Daily report.

All of them were asked by customs officers questions such as whether they received scholarships during their undergraduate studies or with funding from Chinese authorities, whether they had joined the army or if they were involved in classified research.

Despite giving negative answers to many of the questions, officers told these Chinese students their F-1 visas were no longer valid and were denied entry to the U.S., according to the paper.

These students are graduates of prestigious universities including Peking University and Tsinghua University, with degrees in majors such as biology, preventive medicine and statistics.

They are currently enrolled in renowned higher education institutes in the U.S. such as Yale University, Johns Hopkins University and the University of Virginia. Some of them received school scholarships, but none of them has taken part in classified research.

U.S. Customs hasn't given explicit reasons why they were deported.

Chinese Foreign Ministry spokesperson Wang Wenbin said on Thursday that the U.S. has been constantly mistreating Chinese students traveling to the U.S. with lawful and valid visas in the past few months, which is politically motivated law enforcement.

"Some of the students were interrogated, confined, forced into confession, induced and even deported without just cause," Wang said.

Wang said the U.S. has politicized and weaponized academic research and repeatedly interrogated, harassed and deported Chinese students, undermining the students' lawful rights and interests.

"It goes against the agreement to promote and facilitate people-to-people exchanges between the leaders of both countries," he said.

Wang also urged the U.S. to withdraw the unjust Proclamation 10043 and stop bullying and restricting Chinese students in the name of national security.

The order was introduced during the administration of former president Donald Trump in 2020 to prevent postgraduate students and researchers allegedly linked to the Chinese military from entering the U.S..