A Japanese daily newspaper has reported that three officials from South Korea’s National Intelligence Service in China were arrested by Chinese authorities and have been detained for three months.

The daily reported from Seoul and cited multiple informed sources to report the detainment of the South Koreans who were collecting information on North Korea.

According to the daily, the three officials entered China on a tourist visa and collected information in Yanbian Autonomous Prefecture before being arrested one by one in June. The medium says it appears that they are being held on charges of spying.