SEOUL (Reuters) - Eight North Korean defectors in China face involuntary repatriation after being detained by Chinese police last month, the Human Rights Watch group and a pastor who has been assisting them said on Monday.

Human Rights Watch said Chinese government authorities detained the eight North Koreans in mid-March during what appeared to be a random road check in northeastern China.

The detention of North Korean defectors in China comes as U.S. President Donald Trump has pressured China to do more to rein in North Korea amid heightened tension over its nuclear and missile programmes.

“By now, there are plenty of survivor accounts that reveal Kim Jong Un’s administration is routinely persecuting those who are forced back to North Korea after departing illegally, and subjecting them to torture, sexual violence, forced labour – and even worse,” Phil Robertson, deputy Asia director at Human Rights Watch, said in a statement, referring to the North’s leader.

Robertson called on China not to deport the would-be defectors.

The United Nations has said China is required under international law not to return defectors to North Korea, where they could face persecution, torture and possibly death.

China says North Korean defectors are illegal migrants who flee their country for economic reasons. North Korea calls them criminals and describes those who try to bring them to South Korea as kidnappers.

Speaking in Beijing, Chinese Foreign Ministry spokesman Geng Shuang said he was not aware of the report and was unaware of the specific situation.

“Some North Korean citizens, due to economic reasons, illegally crossed China’s border. This violates Chinese law,” Geng told a daily news briefing.

“China consistently handles this kind of issue prudently and appropriately according to domestic and international law, and humanitarian principles,” he added, without elaborating.

The eight North Koreans were in the city of Shenyang, where traffic police stopped their vehicle and took them to a police station because they did not have valid documentation, Human Rights Watch said.

A Christian pastor helping North Korean defectors in China, who declined to be identified, said they had sent him a video clip asking U.S. President Donald Trump and Chinese President Xi Jinping for help.

The video shows North Korean defectors waiting in a vehicle outside a Chinese police station.

“President Trump and Chinese President, please save us. If we go back to North Korea we will be dead,” said a woman whose face was blurred for security reasons.

Another woman sitting next to her put her hands together and pleaded for help.

Scores of North Koreans attempt to flee their country every year, often first crossing into China and then making their way to Southeast Asia. Some countries in the region have worked with South Korea to send them to South Korea.

About 30,000 have made their way to South Korea, many with the help of South Korean human rights groups, religious organisations or commercial brokers.