Seoul, South Korea (Reuters): A Korean government official said on Saturday that China has expelled 32 South Korean Christian missionaries following diplomatic tensions between the two countries over the planned deployment of a U.S. missile defense system in the South.

South Korean media have reported that the 32 missionaries were based in China's northeastern Yanji region near the border with North Korea, many of whom had worked there more than a decade.

South Korea's foreign ministry said on Friday it briefed Christian groups on the case of the missionaries, adding that they were expelled in January.

It said that the ministry advised the groups on the importance of complying with the laws and customs of the areas where they work.

In South Korea, China is widely believed to be retaliating against Seoul's plan to host the Terminal High Altitude Area Defence (THAAD) system of the U.S. military, against the threat of the missile attack from North Korea.

The South Korean government official said that there was no indication of a direct link between the expulsions and tension over THAAD.

"There was no official explanation from China," he said. "There is no confirmation that it is related to THAAD."

China's Communist Party stated that it always protects freedom of religion, but keeps a tight rein on religious activities and allows only officially recognized religious institutions.

According to South Korean media, the number of Korean missionaries working in China might top 1,000. Most are in the northeast, and many help defectors flee North Korea and travel to third countries, including the South.

THAAD's radar is capable of penetrating Chinese territory. Beijing has objected to the planned deployment, saying it will destabilize the regional balance of security, threaten China's security and do nothing to ease tension on the Korean peninsula.

Many South Koreans believe Beijing is retaliating against THAAD, with measures against some companies and cancellations of performances by Korean artists.

South Korea's Lotte Group said on Wednesday that Chinese authorities had halted construction at a multi-billion dollar real estate project after a fire inspection.