The man, named by prosecutors as Jian G., is suspected of working with Chinese intelligence since 2002, including while he was an aide to the Alternative for Germany (AfD) MEP Maximilian Krah between 2019 and 2024.

Krah was the party's top candidate in last year's European elections, but was excluded from its delegation after comments in which he minimised the crimes of the Nazis' notorious SS.

Krah has since been welcomed back into the AfD fold and was elected as an MP in the German parliament in February's snap general election.

Prosecutors said in a statement that Jian G., a German national, used his job as Krah's assistant to "gather information on the deliberations and decisions of the European parliament" for Chinese intelligence, including "procuring more than 500 documents, some of which had been classified as particularly sensitive".

He is also suspected of gathering intelligence on leading AfD politicians and spying on Chinese dissidents in Germany.

This included posing as an opponent of the Chinese government on social media in order to gain contacts in the opposition scene.

The European Parliament, which had listed Jian Guo as an accredited assistant to Krah, moved to suspend the aide after his arrest in April 2024.

Prosecutors said a Chinese national named as Yaqi X. has also been charged with helping Jian G. to access information on flights and passengers at Leipzig Airport.

She worked at a company which provided the airport with logistics services.

The information she passed on focused on flights transporting defence equipment and "people with links to a German arms company".

At the time of her arrest in October, news site Der Spiegel reported that Yaqi X. had in particular targeted the arms giant Rheinmetall, which is involved in making Leopard tanks and which uses Leipzig airport for cargo flights.

Krah's various scandals have not dampened his political fortunes -- or indeed those of the AfD more widely.

In February's election the party had its best-ever performance, doubling its vote share to more than 20 percent and becoming the second-biggest group in parliament, with 152 seats out of a total of 630.