Nine North Korean refugees detained by China are being transferred to a border area in preparation for repatriation despite pleas from South Korea, reports said Friday.

The nine are among dozens of North Koreans detained by Beijing this month in an intensifying crackdown on refugees from the impoverished country.

The South's foreign ministry and human rights groups have urged Beijing not to send them back against their will, saying they may face harsh punishment.

But China is transferring nine to the northeastern border city of Tumen for immediate repatriation and plans to send an unspecified number of other refugees back by early next week, Dong-A Ilbo newspaper said, citing sources in Seoul.

Park Sun-Young, a conservative opposition lawmaker, told Yonhap news agency that China was transferring the nine to Tumen and plans to repatriate 10 others held in Shenyang plus five from Changchun.

In addition a family of three North Koreans was captured by Chinese authorities in Longging on February 13, she said, and would also be returned.

China's policy is to treat North Koreans found on its soil as economic migrants and to send them home, even though they risk severe punishment.

Rights groups criticise the policy, saying they should be given refugee status.

More than 21,700 North Koreans have fled to South Korea since the 1950-1953 war, the vast majority in recent years. They almost always escape on foot to China, hide out and then travel to a third country to seek resettlement in Seoul.

The North has strengthened border security and toughened punishment for refugees since its young new leader Jong-Un took over from his late father Kim Jong-Il in December, according to activists.