A group of Muslims who fled China after deadly ethnic rioting and sought asylum in Cambodia were sent back home Saturday, even though rights groups fear they face persecution and possibly execution there.

Interior Ministry spokesman Lt. Gen. Khieu Sopheak said the 20 members of the Uighur minority had been put on a special plane sent from China that left Phnom Penh International Airport Saturday night.

"They are going back to China," he said.

Cambodia has been under intense pressure from China to deport the Uighurs, whom Beijing has called criminals after they fled the country with the help of a secret network of missionaries. The expulsion came a day before Chinese Vice President Xi Jinping visits Cambodia as part of a four-country tour.

The United States, the United Nations and human rights groups had urged Cambodia to stop the deportation. A spokeswoman for the U.N. refugee agency said it had not finished evaluating the Uighurs, including two children, for refugee status. She said the agency had stationed people at the airport in an effort to physically prevent the deportation. The plane, however, left from the airport's military area.

"Even if I say something, can we change anything?" Ilshat Hassan, a U.S.-based director of the World Uyghur Congress, said after the deportation. "The UNHCR, the international world, the U.S., everybody who said something that could give us hope. They all failed."

The Uighurs were being deported because it was determined they entered the country illegally, Foreign Ministry spokesman Koy Kuong said earlier. He said two other Uighurs who had been with the group are missing.

Some countries have refused to send Uighurs — such as those released from U.S. detention at Guantanamo Bay in Cuba — back to China over concerns about retribution and abuse. In a letter to the Cambodian government about the Uighurs, rights group Amnesty International noted that Shaheer Ali, a U.N.-recognized refugee, was executed after being forced to return to China from Nepal in 2002.

"It is hugely concerning that Cambodian authorities are not giving this group an opportunity to seek asylum, or for authorities to assess their asylum case," Brittis Edman, a Cambodia researcher with Amnesty International, said late Saturday before the group left. "This group will be particularly vulnerable to torture."

A woman answering the phone at China's Foreign Ministry on Saturday night said they had no immediate comment on the Uighurs' deportation.

Uighurs say Beijing has long restricted their rights, particularly clamping down on their practice of Islam.

Tensions between majority Han Chinese and the Turkic Uighurs in their traditional homeland in far western China exploded into rioting in July, the country's worst communal violence in decades. The Chinese government says nearly 200 people, mostly majority Han Chinese, died.

Exile groups say Uighurs have been rounded up in mass detentions since the rioting. China has handed down at least 17 death sentences — mostly to Uighurs — over the violence.

The Uighurs arrived in Cambodia in recent weeks and had initially been in joint custody of the U.N. refugee agency and Cambodian authorities. Khieu Sopheak said they had been shifted to the "sole protection" of the Cambodian government.

"I think we went to extraordinary lengths to prevent deportation. But it comes down to, it's up to states to provide protection," said Kitty McKinsey, spokeswoman for the United Nations High Commissioner for Refugees in Bangkok. "We had people prepared to try to physically prevent the deportation if it had taken place at the civilian side of the airport."

McKinsey said the refugee agency is preparing a protest to the Cambodian government.

The United States also urged Cambodia not to send the Uighurs back to China.

"We are deeply disturbed by the reports that the Cambodian government might forcibly return this group of Uighurs without the benefit of a credible refugee status determination process," U.S. Embassy spokesman John Johnson in Phnom Penh said earlier. There was no immediate U.S. reaction to the actual expulsion.

Chinese Foreign Ministry spokeswoman Jiang Yu said last week the Uighurs were "involved in crimes." She did not elaborate.

Wang Lixiong, a China-based writer on Uighur and Tibetan issues, said the deportation reflected China's powerful influence in the region. China says it is the top foreign investor in Cambodia.

"When I learned the Uighurs landed in Cambodia, I was pessimistic because Cambodia is a small country that will not be able to stand against China's pressure," said Wang.