Beijing said Tuesday a group of North Koreans arrested in China and facing repatriation were illegal economic migrants and not refugees deserving protection, as Seoul battles to rescue them.

At least 10 North Koreans who crossed into China and perhaps as many as 30 will be sent back to the secretive state, even though they face harsh punishment in their homeland, activists and Seoul lawmakers have said.

"The relevant people entered China illegally due to economic reasons. They are illegal border crossers, they are not within the category of refugees," foreign ministry spokesman Hong Lei told reporters.

"This issue does not fall under the relevant UN mechanism."

His remarks came after South Korea's foreign ministry said it would seek global support for ensuring the safety of the North Koreans at a meeting next week of the United Nations High Commissioner for Refugees (UNHCR).

Activists and lawmakers in Seoul say around 30 North Koreans will be repatriated.

But South Korea's foreign ministry has only confirmed that 10 North Koreans face being sent back after being arrested in the northeastern city of Shenyang this month, and says it has repeatedly urged Beijing against the repatriation.

"Since our bilateral discussion (with China) is not working very well, we will make efforts to get international support via various channels including the UNHCR," a spokeswoman told AFP.

Activists have assailed China's policy of repatriating North Koreans as economic migrants rather than giving them refugee status, saying they face "indefinite torture eventually ending with public execution" if sent home.

Despite the risks, more than 21,700 North Koreans have fled since the 1950-1953 Korean War -- the vast majority in recent years.

They typically escape on foot to China, hide out and then travel to a third country to seek resettlement in South Korea.

The Seoul spokeswoman also confirmed a media report that 11 North Korean refugees have been trapped in South Korean consulates in Beijing and Shenyang for almost three years because China refuses to let them leave for the South.