An underground network of Christian missionaries that usually works with North Korean refugees says it has helped smuggle nearly two dozen Muslim Uighurs out of China following last summer's deadly ethnic violence and the subsequent government crackdown.

It's the first time the Christian interfaith network has worked with a group of Uighurs, and it won't be the last, with more currently using the so-called underground railway to make their way out of the country and requests for assistance surging into the hundreds, missionaries said.

Long-simmering tensions between Turkic Uighurs and China's Han majority have increased since July's riots in the western region of Xinjiang. The Chinese government says the violence left nearly 200 people, mostly Han, dead.

A Chinese court sentenced three Uighurs to death Friday for their actions during the rioting, bringing to 17 the number of death sentences handed down over the violence. Overseas Uighur groups say Uighurs have been rounded up in mass detentions since the riots.

Some have turned to the "railway" for help, and one Macau-based missionary who is part of the network said they now have daily contact with major Uighur exile groups.

The network of sympathetic Chinese Christians shelter and guide people, usually North Koreans, as they cross China on their way to UN refugee offices abroad to seek asylum.

The first group of 22 Uighurs, who've been described by exile groups as witnesses to the rioting, made their way through China and Vietnam before arriving over the past few weeks in the Cambodian capital, where they have made contact with the UN refugee office and applied for political asylum.

However, they live in fear of being picked up and returned to China, which has close ties with Cambodia, Uighur groups said.

"China has a very big influence in Cambodia. So their life is in risk, I would say," said Ilshat Hassan, the U.S.-based director of interior affairs for the World Uyghur Congress.

A spokesman for China's Foreign Ministry asked that questions about the 22 Uighurs be sent in a fax, and offered no immediate response Friday. The Public Security Bureau in Xinjiang did not immediately respond to a faxed request.

Hassan said the group is the first large one to leave China after the riots. Two other Uighurs were arrested in Vietnam, he said, and he lost contact with another group of four.

A spokesman for Cambodia's Ministry of the Interior, Pol. Lt. Gen. Khieu Sopheak, said Friday that at least 16 Uighurs are staying at the office of the United Nations High Commissioner for Refugees in Phnom Penh. The office is the closest UNHCR office to China in Southeast Asia.