The arrests came a week after German Chancellor Olaf Scholz travelled to China to press Beijing on its support for Russia's wartime economy after the invasion of Ukraine and to raise issues of intellectual property theft and fair market access.

Germany, which considers China both a partner and a rival, is also concerned about China exporting dual use goods to Russia which can be deployed on the battlefield.

Prosecutors identified the suspects as Herwig F. and Ina F, a married couple who run a company in Dusseldorf, and Thomas R., whom prosecutors described as an agent for an employee of China's Ministry of State Security (MSS).

Through their company, the couple concluded a co-operation agreement with a German university.

Part of that agreement involved preparing a study for a Chinese contractual partner on machine parts that can be used for the operation of powerful marine engines such as combat ships, prosecutors said in a statement.

The Chinese contract partner was the MSS employee from whom Thomas R. received his orders, it added.

The suspects also purchased a special laser from Germany on behalf of and with payment from the MSS and exported it to China without authorisation, according to the prosecutors, who did not specify what the laser could be used for.

Last year, Scholz's government presented a strategy paper referring to China as both a key trade partner and a systemic rival. It also warned companies and research institutes about the threat of cyber and hybrid security risks from China.

The Chinese embassy in Berlin did not immediately respond to a request for comment.

Last week, Germany arrested two Russian-German nationals on suspicion of spying for Russia. They are said to have plotted sabotage attacks aimed at undermining Germany's military support for Ukraine in its war against Russia.

Monday's arrests were made on the basis of intelligence gathered by Germany's domestic intelligence agency, prosecutors said.