Human rights watchdog Amnesty International urged China on Wednesday not to repatriate North Korean refugees, joining growing calls by South Korea and members of the global community.
Activists and Seoul lawmakers say about 30 North Koreans who recently fled to China will soon be sent back. They face harsh punishment or even death in their homeland, according to the activists.
Some have already been returned, according to local media reports.
Amnesty said in a statement returnees are sent to labour camps where they are subject to "torture and other cruel, inhumane, or degrading treatment". It cited former detainees it had interviewed.
Activists say the North has strengthened border security and toughened punishment for defectors during the politically sensitive power transfer from the late leader Kim Jong-Il to his son, Jong-Un.
"The reported denunciation of border-crossers by North Korea's new government... could signal that those returned may be subjected to even harsher punishment than usual," said Amnesty's Korea expert, Rajiv Narayan.
"The Chinese authorities must also stop breaking international law and cease forcibly returning people to a country where they face persecution, torture and death."
Seoul has repeatedly called on Beijing to treat fugitives from the North as refugees and not to repatriate them. China says they are economic migrants and not refugees deserving protection.
A Seoul parliamentary committee on Monday passed a resolution that criticised China's policy. The UN refugee agency UNHCR on last Friday also urged Beijing not to send the refugees back.