BEIJING — The last time Abdulhamid Tursun spoke to his wife, she was huddled in a Beijing hotel room with their four children, frightened after being evicted from the Belgian Embassy in the dead of night. Suddenly, plainclothes police officers burst into the room, cutting off the couple’s video call.
Mr. Tursun says he has not heard from her since.
His wife, Wureyetiguli Abula, 43, had gone to the Belgian Embassy to seek visas so the family — from the Uighur Muslim minority group — could be reunited with Mr. Tursun, 51, in Brussels, where he won asylum in 2017.
But instead of finding protection, Ms. Abula and her children, ages 5 to 17, were dragged away after the Chinese police were allowed to enter the embassy.
Now the case is raising alarms back in Belgium, where lawmakers are asking how it could have happened and where Mr. Tursun’s family has been taken. It illustrates how, two years after China began detaining Uighurs in a vast network of internment camps, the group has limited protections — even from Western democracies — against persecution by the Chinese government.
Even Uighurs who make it to the West have not always been safe. Early last year, Germany mistakenly sent back to China a 22-year-old Uighur asylum seeker, who has not been heard from since.
On Monday, Belgium said it was sending a special envoy to Beijing to clarify the whereabouts of Mr. Tursun’s family. The Belgian government also said its ambassador in Beijing would try to secure passports for Ms. Abula and the children.
In Beijing, a spokesman for the foreign ministry, Lu Kang, said at a regularly scheduled news briefing on Tuesday that he had no knowledge of the case.
China has sent around one million Uighurs to internment camps in Xinjiang, the semiautonomous region in western China where most of them live. The figure is equivalent to about one-tenth of the region’s Uighur population.
The government asserts that the Uighurs represent a terrorism threat to China and the world, an argument that is disputed by many Western nations, who see the internment effort as a systematic abuse of human rights. Some Uighurs who managed to leave the camps have told of being subjected to intense indoctrination under armed guard.
Uighurs outside the camps have seen their cities and homes turned into virtual prisons thanks to surveillance technology and a heavy military presence.
The Belgian Embassy’s handling of the case has come under criticism. Under international law, governments are obliged not to send people to countries where they are at substantial risk of being tortured, said Sarah H. Cleveland, a professor of law at Columbia University. Given that Ms. Abula and her children are Uighur, it was incumbent upon the Belgian Embassy to assess that risk, she said.
Ove Bring, a Swedish expert on human rights law, also said that Belgium appeared to have breached accepted standards of care. “Belgium could be criticized on grounds of international morality, having refused to offer humanitarian protection,” he said.
Since China intensified its crackdown in Xinjiang, some Western European countries have taken precautions to stop Uighurs who seek asylum from being sent back to China. Germany and Sweden said last year that they would refrain from deporting Uighurs.
Ms. Abula arrived in Beijing at the end of May, and on the advice of a nongovernmental organization in Belgium sought visas at the embassy that would allow the family to join Mr. Tursun in Brussels, where he works at an electronics company. He had been granted asylum in Belgium in late 2017 after his brother was arrested and placed in a detention camp.
The family group did not hold Chinese passports. But Mr. Tursun said his wife had been told by CAW, a Belgian group that helps immigrants, that along with the visas she and the children would each be issued a substitute travel document known as a laissez-passer.
At the embassy, Ms. Abula was told that the visas would take longer than she expected. Laissez-passer papers could not be issued because China does not recognize such documents, Matthieu Branders, the spokesman for the Belgian foreign ministry, said in response to written questions.
Scared and frustrated, Ms. Abula told embassy officials that she planned to remain on the grounds after their offices closed, according to Vanessa Frangville, a professor of Chinese studies in Brussels who has worked on the case.
When Ms. Abula settled into the front yard with her children, the staff complained that she was staging a “sit in,” Mr. Branders said. They offered to drive her to her Beijing hotel in a diplomatic vehicle, he said. But Ms. Abula had already been harassed there by the police and was too afraid to return, Ms. Frangville said.
Soon after midnight on May 29, the police arrived at the embassy and disappeared inside, Mr. Tursun said, recounting what his wife and eldest daughter told him via the messaging app WeChat as events unfolded.
After about an hour, the police drove into the embassy yard, forced Ms. Abula and the children into the car and headed for a nearby police station, Mr. Tursun said.
It is unclear who called the police to the Belgian Embassy, who authorized them to enter, and who asked for Ms. Abula and her children to be removed. Asked on several occasions who let the police onto the embassy grounds, Mr. Branders declined to answer.
By midmorning that day, police officers from Xinjiang had taken charge of the family and transferred them back to the hotel, where they were left alone for a day.
Then on May 31, the plainclothes officers entered the room. “It’s you guys again,” Ms. Abula said, in Mr. Tursun’s recounting. She recognized them from the ordeal at the embassy, he said. Then her cellphone went dead.
Days later, Mr. Tursun learned through a friend that four male and three female police officers had guarded the family as they drove for about 30 hours across China back to their home in Urumqi, the capital of Xinjiang.
His wife was now under house arrest, and the electronic equipment Mr. Tursun had left in the house had been confiscated by the police, the friend told him.
Upset that his family’s plans had gone so awry, Mr. Tursun, accompanied by Ms. Frangville, met with Josef Bockaert, the director of consular affairs at the Ministry of Foreign Affairs in Brussels.
During the meeting, Mr. Tursun asked the Belgians to press the Chinese about what happened to his family, he said. At one point, Mr. Bockaert replied that Belgium was a small country and could not risk putting too much pressure on China, Ms. Frangville recalled.
“We don’t want to be in conflict with China,” Ms. Frangville quoted Mr. Bockaert as saying. Asked if Mr. Bockaert had made the comment, the spokesman, Mr. Branders, declined to answer.
Belgium has cultivated warmer economic and diplomatic relations with China in the past year. In December, the e-commerce giant Alibaba agreed to invest in logistics infrastructure in the country, a project involving a big lease at the Liège cargo airport, and the first of its kind for the Chinese company in Europe.
The roughly 200 Uighurs who live in Belgium are treated well, Ms. Frangville said, and asylum is granted to those who request it when they arrive.
But she said it was astonishing that the police in Beijing were allowed onto the embassy grounds.
“Someone opened the door,” she said. “The Belgian Ministry of Foreign Affairs won’t say who allowed them in. Why such a mystery?”