Human Rights Watch has sent a letter to China accusing it of violating international law by forcing thousands of Burmese to return to their conflict-torn homeland.
The group says Beijing recently returned at least 4,000 ethnic Kachins who had fled to China's Yunnan province. It says they were sent home in late August after the government "summarily declared" they were not refugees.
Tens of thousands of people have fled fighting in northern Burma since June 2011, when a 17-year cease-fire between the military and the Kachin Independence Army collapsed.
China has denied forcibly returning the Kachins, saying they voluntarily returned to Burma when the fighting ended. But Human Rights Watch says the violence continues in Kachin state and that thousands more are being displaced.
The group's letter to the Chinese Foreign Ministry says up to 10,000 Kachin refugees who have been allowed to enter China have not been provided humanitarian assistance and have been denied access to United Nations human rights officials.
Bill Frelick, refugee program director at Human Rights Watch, says China is creating "its own refugee status determination process" rather than honoring international law on refugees.
Last week, the U.S. State Department called on China to give temporary protection for Kachin refugees in Yunnan, saying they should only return home by their own choice and when it is safe to do so.
Burma's government has reached cease-fire deals with several ethnic minority rebel groups in recent months. But negotiations with the Kachin have so far been unsuccessful.