Gui Minhai, a former Swedish national and Hong Kong bookseller, was sentenced to 10 years behind bars on Monday for "illegally providing intelligence overseas."

According to court statement by the Intermediate People's Court of Ningbo, the 55-year-old pleaded guilty to the charge and said he would not appeal at the end of the trial. He has also been sentenced to deprivation of political rights for five years.

Shortly after the ruling, Beijing spoke up, saying what Gui had done has "greatly damaged the interest of China."

"As a law-governed country, China will strictly run every criminal case based on laws. We will fully preserve the legal rights of Gui Minhai," said Foreign Ministry Spokesperson Zhao Lijian on Tuesday. 

"We strongly oppose foreign interference on China's internal matters," he said.

Gui, born in China, became a naturalized Swedish citizen in the early 1990s. He resumed his Chinese citizenship in 2018, which means that he automatically gave up his Swedish citizenship as China does not recognize dual citizenship.

According to the Beijing official, visits to Gui have been temporarily suspended due to the novel coronavirus outbreak, an epidemic that has claimed lives of over 2,660 people within China.