North Korean soldiers patrol the Yalu River on the Chinese-North Korean border

Two South Korean pastors have been arrested by Chinese police for giving protection to North Korean defectors in China, reports the South Korean news agency, Yonhap.

The anti-North Korean campaign group, Justice for North Korea, said that the two pastors were helping defectors at risk of being repatriated. The pastors were detained for helping the defectors leave China.

The South Korean Foreign Ministry says they are in a detention centre in the north-east of China, and have consular help. Both were arrested with other family members, who were then released after two days’ interrogation. The arrests came amid strained relations between Beijing and Seoul over the deployment in South Korea of an advanced missile-defense system, called THAAD, by the United States, which China says is against its strategic interests.

In February, 32 South Korean missionaries were expelled from China’s border region with North Korea. The move was also seen as retribution for South Korea’s decision over THAAD.

At the time of the mass expulsion, South Korea’s foreign ministry advised Christian groups about the importance of complying with Chinese laws and customs. There are thought to be 1,000 South Korean missionaries working in China, many in the border region with North Korea.