Amnesty International on Wednesday urged China not to repatriate 21 North Korean asylum seekers at risk of imprisonment and possibly execution if they return to their country. Chinese authorities were believed to be holding the North Koreans in the north-eastern city of Changchun and planned to expel them by Monday for illegally entering China, the London-based group said. 'If returned, they are at risk of detention, torture and even execution as illegal border-crossers,' Amnesty said of the North Koreans, who were arrested February 8 at several locations in nearby Shenyang. Like thousands of other North Koreans who cross the 1,400-kilometre border into China, they were attempting to reach South Korea. China refuses to recognize North Koreans as asylum seekers and instead counts them as economic migrants. The death of Kim Jong Il in December and his succession by his son, Kim Jong Un, as leader of the famine-hit nation have prompted threats of harsher punishments against North Korean defectors, Amnesty said. 'The Chinese authorities must enable these 21 North Koreans to seek asylum in China and other countries and provide them with access to the UN refugee agency or other relevant refugee channels,' said Sam Zarifi, Amnesty International's Asia-Pacific director. From 30,000 to 300,000 North Korean migrants remain in limbo in China, according to widely varying estimates. Most of them are women. Some of the refugees reach South Korea via underground networks run by rights groups, Christian organizations and human traffickers, usually after an overland trek though China into Laos, Myanmar, Vietnam or Thailand. About 23,100 North Koreans have settled in South Korea since 1998 while a few hundred have gone to the United States, Canada and other Western nations. The South Korean government said 2,737 North Korean refugees arrived in the country last year.