SEOUL, March 8, 2010 (AFP) - Some 50 North Korean refugees are taking refuge in South Korean diplomatic missions in China, living like prisoners because of security concerns, a Seoul rights group said Monday.

Up to 30 of the total have stayed more than one year in the Beijing embassy or consulates elsewhere, said the Citizen's Coalition for Human Rights of Abductees and North Korean refugees.

"The embassy restricts their movement and communication with relatives outside because of tight security and surveillance by Chinese police," coalition head Do Hee-Yeun told AFP.

"They are living like prisoners inside," he said, adding China had intentionally delayed negotiations with South Korea about their departure to Seoul to show that the embassy is not a safe refuge.

Virtually all North Korean refugees cross into China, but face forced repatriation if caught there and the risk of harsh punishment in their home country.

Beijing's policy of treating the refugees as economic migrants has been strongly criticised by rights groups.

The plight of refugees sheltered in the embassy has prompted South Korea's state human rights watchdog to start a probe.

Activists claim Seoul has not been eager to address the issue for fear of creating diplomatic strains with Beijing. They have called for permission to exchange letters with North Korean refugees inside the embassy.

The South's foreign ministry gave no figures but said it was trying hard to bring the refugees to Seoul and to improve their living conditions inside the mission.

Many refugees leave China and travel on to Southeast Asian nations in the hope of eventual resettlement in South Korea.

About 18,000 North Koreans have arrived in the South since the end of the 1950-1953 Korean War, the vast majority in recent years.