US authorities say they have uncovered “a broad and significant” cyberespionage campaign carried out by China-linked hackers aiming to steal information from Americans working in government and politics.

The FBI and the Cybersecurity and Infrastructure Security Agency (CISA) said in a joint statement on Wednesday that actors affiliated with Beijing had “compromised networks at multiple telecommunications companies”.

The hack enabled the “theft of customer call records data” and compromised the “private communications of a limited number of individuals”, the agencies said.

The FBI and CISA did not specify which individuals had been targeted but said they were “primarily involved in government or political activity”.

The hackers also accessed “information that was subject to US law enforcement requests pursuant to court orders”, the agencies said, suggesting they sought to compromise programmes subject to the Foreign Intelligence Surveillance Act (FISA), which grants spy agencies broad powers to surveil the communications of individuals suspected of being foreign agents.