Beijing has accused two Chinese citizens of spying for Britain, adding to the tensions between the two nations.

China and Britain have been at odds over Beijing’s suppression of free speech and elections in Hong Kong, a former British territory.

The Ministry of State Security in China revealed on social media that it had uncovered an espionage case involving a couple, identified only as Wang and Zhou, who were allegedly recruited by Britain’s MI6.

Wang had gone to Britain as a student in 2015 and was later joined by his wife. They allegedly received financial incentives and other benefits from MI6 and passed government secrets to the agency.

The investigation is ongoing, and the couple’s whereabouts are unknown. Britain has not commented on the accusations, NBC News reported.

Meanwhile, Britain announced last month that two men would face trial for allegedly collecting sensitive information for Hong Kong authorities, and a third suspect was found dead under unexplained circumstances.

Written by B.C. Begley