A Chinese court in the southeastern city of Suzhou has sentenced a 78-year-old United States citizen to life imprison on spying charges. The local bureau of China's counterintelligence agency had arrested him on April 15, 2021 a news release from the court said.

John Shing-Wan Leung was convicted of espionage charges by the Intermediate People's Court on Monday. According to the court's statement on its WeChat social media account, his personal property was also confiscated.

Leung is a permanent resident in Hong Kong. At the time of his arrest, the media could not establish where he was living.

He joins a growing list of foreign nationals who have been convicted on espionage charges under Xi Jinping's leadership, CNN reported.

Chinese officials have not given further details about why Leung was detained or what led to his conviction. Legal observers say that sensitive cases concerned with state security such as espionage are usually held behind closed doors in China.

In a press conference on Monday, Hong Kong's Secretary of Security, Chris Tang, told that the city was already notified of Leung's arrest in 2021.

The U.S. Embassy in Beijing said it was aware of Leung’s sentencing, asserting that the Department of State has no greater priority than the safety and security of U.S. citizens overseas.

Last month China passed key amendments to heighten national security. The new legislation which will come into effect on July 1, and will ban possession of data that authorities feel can harm national security. Chinese security agencies have in the past stormed offices of foreign consulting businesses that provide sensitive economic data, Associated Press reported.

Leung’s sentencing comes at a time when the relationship between the U.S. and China is at its lowest point.

Beijing and Washington strained relationship

The relations between the two countries has deteriorated over time especially during the administration of Donald Trump. According to AP, the strained relationship is because of issues arising from trade, technology, human rights and China’s increasingly aggressive approach toward its territorial claims involving self-governing Taiwan and the South China Sea.

An alleged spy balloon which the U.S. shot down earlier this year is also perceived to have increased the tension.

Many foreign nationals have been arrested due to espionage in China

Apart from Leung's recent imprisonment, many foreign nationals have been arrested in relation to espionage charges. In March, an employee of the Japanese pharmaceutical company Astellas Pharma was detained in Beijing by Chinese authorities on suspicion of espionage. In total, 17 Japanese citizens have been arrested since the counter-espionage law was introduced in 2014, according to AP.

Former diplomat Michael Kovrig and businessman Michael Spavor were detained in 2018 and remained in prison for almost three years. Their arrest came after Canada arrested Huawei executive Meng Wenzhou on a U.S. warrant. Beijing maintained it was not a political retaliation.