A former employee working for one of China's state agencies has been given a rare death sentence for leaking "state secrets," the Ministry of State Security said on Wednesday after he was accused of handing over his USB drive to foreign spy agencies.

The case underscores China's intense crackdown on espionage activities and highlights escalating tension between China and other countries on national security issues.

A man surnamed Zhang provided a "large number of top-secret and confidential state secrets to foreign spy intelligence agencies, seriously endangering China's national security", the ministry posted on messaging application WeChat.

It did not reveal his full name or his previous job position. Reuters was unable to contact Zhang for comment.

Zhang was once "a core confidential personnel of a state agency" and was exposed to a large number of state secrets at work, the ministry said.

After leaving his job, Zhang became an "important target for foreign spy intelligence agencies to win over and subvert".

"Zhang, who was weak in character and could not resist the temptation of money, became a 'puppet' controlled and used by the other party," the ministry said.

Zhang travelled outside of China to meet with a foreign spy surnamed Li who forced him to sign a cooperation agreement. Li seized Zhang's USB work flash drive and personal belongings, the ministry said.

After receiving training from the foreign spy agency, Zhang became "a secret-stealing black hand controlled and used by the foreign intelligence agency".

Chinese lawmakers passed a wide-ranging update to Beijing's anti-espionage legislation in April, banning the transfer of any information related to national security and broadening the definition of spying.

In a separate case earlier this year, a Beijing court handed Australian writer Yang Hengjun a suspended death sentence on espionage charges in February, a decision the Australian government described as "harrowing".

A suspended death sentence in China gives the accused a two-year reprieve from being executed, after which it is automatically converted to life imprisonment, or more rarely, fixed-term imprisonment. The individual remains in prison throughout.

In Zhang's case there was no mention of a suspended death sentence.