In addition to stealing trade secrets and intellectual property, the hackers may be trying to penetrate customers' and service providers' networks to infiltrate several companies at once, the BfV said in a circular to companies.

In its annual constitutional protection report from 2019, the BfV had pointed out the group's acronym APT 27 is an alias for a Chinese hacker group also known as the "Emissary Panda," which is believed to target foreign embassies and critical sectors.

Last year, the United States and its allies accused China of a carrying out a global cyberespionage campaign. China has denied the allegation.

(Reporting by Zuzanna Szymanska; Editing by Mark Potter)