Vitit Muntarbhorn, the UN spokesman on human rights in North Korea, says the international community should lean on China to uphold its legal obligations.
As China is a party to the International Refugee Convention, it "should be supported well to implement its obligations under that convention," he said.
"The people coming from the DPR Korea (North Korea) fear persecution upon return to their country of origin," Mr Vitit said.
"As such, they are refugees and "should be dealt with and respected accordingly," he said.
US Republican Senator Sam Brownback last month threatened to seek sanctions against China if it did not stop turning back refugees from North Korea.
"Thousands are fleeing persecution and starvation only to be rounded up by the Chinese in contravention of international law and returned to North Korea to persecution and probable death," Mr Brownback said.
Mr Vitit was appointed last July to investigate human rights violations in North Korea and to begin a dialogue with its government.
"I've tried to be very constructive, I've tried to be polite, courteous and I've tried to contact the North Korean authorities but regrettably I've not been allowed into the country," Mr Vitit said.
Earlier this year, North Korea rejected a UN resolution criticising human rights violations, saying it was part of a US-led "hostile" campaign and was "politically-motivated".
- Australian Broadcasting Corporation
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