North Korean officials who failed to prevent recent defections have been mown down by anti-aircraft fire in grotesque executions ordered by leader Kim Jong Un, a South Korean report said Thursday.

Citing a source, the Yonhap news agency said Kim has also moved to strengthen controls over North Koreans overseas, assigning additional security agents to monitor government missions and citizens traveling on business trips.

Kim has also ordered the families of North Korean diplomats and workers to return home after the defection of Thae Yong Ho, the deputy ambassador to London, who fled to Seoul with his wife and child. This gives the regime “hostages” to discourage defections, Yonhap’s source said.

Thae’s defection is one of the most high-profile ever for Pyongyang. However, he is just one in a steady stream of defectors choosing a new life in the South.

In April, wait staff and their manager escaped from a North-run restaurant in China. Pyongyang accused the South of kidnapping them; Seoul responded by placing them in protective custody, releasing them on Wednesday to begin the formal process of resettlement.

Few North Koreans get the chance to travel abroad, but the government grants permits for those likely to bring revenue to the state.

“Kim has threatened an immediate pullout of overseas business operations that fail to perform,” Yonhap’s source said.