Three German citizens, a married couple from Düsseldorf and a man from Bad Homburg, have been arrested on suspicion of spying on behalf of China, prosecutors have said, in the second high-profile alleged espionage case reported in the country in days. The three are accused of passing on technical military knowhow to Chinese authorities in return for money. The head of Germany’s domestic intelligence agency said it could be “just the tip of the iceberg” of spy rings operating in Germany. In one case, prosecutors allege, the trio exported a laser bought in Germany to China without the required permissions. Information on machine part technology that could be used in warships was allegedly also sent to China. The couple, identified as Herwig and Ina F, are believed to have been employed by a company affiliated to a university, and the man, identified as Thomas R, is thought by prosecutors to have acted as a liaison with the couple. All three are thought by prosecutors to have been recruited by the Chinese secret service, the Ministry of State Security (MSS), at some point after 2002 in mainland China and been operational until at least June 2022. The arrests come just days after the arrest of two German Russians who were allegedly spying on behalf of Russia, scouting out military bases – including US posts used for training Ukrainians in the operation of Abrams tanks – with a view to carrying out explosive attacks on them. Thomas Haldenwang, the president of Germany’s domestic intelligence agency, the Federal Office for the Protection of the Constitution, told a press conference on Monday the trio were “involved in carrying out fictitious transactions to conceal their activities” and that “goods were either not declared or were exported via third countries”. He said it was believed their motivation was “purely monetary” and, according to prosecutors, the trio were paid in the upper five-figures for relevant information they passed on. Haldenwang said his office believed the alleged spy ring was one of many similar ones operating in Germany. German media reports said Thomas R spoke fluent Mandarin and was married to a Chinese woman, while the married couple are reported to have lived and worked in an 18-storey apartment building in Düsseldorf where their company was also registered. The accused were arrested early this morning, and crime investigators were searching their home and workplaces. Universities have long been seen as a weak point in the German authorities’ attempts to clamp down on Chinese industrial espionage in Germany. According to media reports, the accused were encouraged to set up research projects that could be useful for a Chinese contract partner, under a so-called “knowledge transfer” agreement. The project was then financed by the Chinese state via its agencies, prosecutors said, and the contract partner was the same MSS employee that Thomas R was allegedly working for. The accused were in discussions at the time of their arrests to launch further research projects relating to China’s planned expansion of its maritime combat operations. Haldenwang said that cases of so-called proliferation were becoming increasingly common, referring to the unauthorised transfer of military material or the technology or relevant knowledge required for its production. He said such incidents were most commonly linked to Iran, North Korea, Russia and China. He said the case uncovered on Monday was typical of what investigators were repeatedly finding. “Those involved put much energy into concealing their activities, for example by carrying out sham transactions, falsely declaring goods or using intermediaries for exports.”