They have identified the man as Jian G, 43, named by German media as an assistant to AfD MEP and European election candidate Maximilian Krah.
Prosecutors say he was arrested in the eastern city of Dresden. They allege he passed information about the European Parliament to Chinese intelligence.
Jian G is also suspected of spying on Chinese opposition figures in Germany.
The allegations come at an awkward time for the AfD (Alternative for Germany), ahead of this year’s European Parliament elections.
Mr Krah said he had learned of his aide’s arrest from the press and that if the allegations were found to be true then his employment would be terminated immediately.
“Espionage for a foreign state is a serous accusation,” his statement said.
A spokesman for the AfD added that reports of “the arrest of one of Mr Krah’s employees on suspicion of espionage are very worrying” and they were waiting for further investigations from the public prosecutor.
Germany’s Interior Minister Nancy Faeser said the allegations were extremely serious: “If it is confirmed that someone spied for China in the European Parliament, this is an attack from within on European democracy.”
Justice Minister Marco Buschmann said “tough consequences” would be required if the accusations proved to be true.
China’s foreign affairs ministry rejected the arrest as speculation designed “to smear and suppress China”. Condemning what he called as “hype”, spokesman Wang Wenbin complained that “the so-called Chinese spy threat theory is not new in the European public opinion field”.
Prosecutors said Jian G was due to go before an investigating judge later on Tuesday.
He had worked since 2019 “for a member of the European Parliament”, they said. But they did not name Mr Krah, who is the AfD’s lead candidate in the European Elections which take place in the EU’s 27 member states from 6-9 June.
One of Mr Krah’s AfD colleagues in the European Parliament, Sylvia Limmer, posted angrily on X that he had been a problem for his Brussels colleague for the past five years, because of “his stance on China, Russia, the USA, Israel, women and much more”.
The number two on the party’s election list, Petr Bystron, has come in for criticism too in recent weeks. He has strongly denied allegations that he received payments from a Prague-based Russian disinformation network closed down earlier this month by Czech authorities.
Jian G’s detention comes a day after two men and a woman were arrested on suspicion of spying for China, by allegedly obtaining information in Germany about military technology for China. The latest case is not believed to be linked.
The main suspect in that case is alleged to have operated a front company working with German research organisations while spying for the Chinese Ministry of State Security (MSS). Thomas R is alleged to have obtained “innovative technologies for military use” on behalf of an MSS employee.
German Chancellor Olaf Scholz returned days ago from an important visit to Beijing where he held talks with President Xi Jinping on issues including Russia’s war in Ukraine.
