US authorities say cybercriminals linked to China may have attempted to tap into the phones or networks used by former President Donald Trump and his running mate, Senator JD Vance, a number of sources familiar with the matter confirmed to the BBC’s US news partner, CBS News.

The sources said the Trump-Vance campaign had been alerted to the fact that phones used by Trump and Vance may have been among the targets of a broader cyber attack.

Official from both major political parties are thought to have been targeted, one source told CBS.

It is unclear how much information, if any, may have been compromised.

The Department of Justice and the FBI declined to comment on whether candidates were targeted.

A joint statement from the FBI and the Infrastructure Security Agency (CISA) said the US government was investigating the “unauthorised access to commercial telecommunications infrastructure by actors affiliated with the People’s Republic of China”.

They said after the “malicious activity” was identified, the agencies “immediately notified affected companies, rendered technical assistance, and rapidly shared information to assist other potential victims,” adding that the investigation was ongoing.

“Agencies across the US government are collaborating to aggressively mitigate this threat and are coordinating with our industry partners to strengthen cyber defences across the commercial communications sector,” they added.

The Trump campaign blamed Democrats for the hack, claiming without evidence that it was an attempt “to prevent President Trump from returning to the White House”.

The Wall Street Journal said people affiliated with the Harris-Walz campaign were also targeted, citing a source familiar with the matter.

Law enforcement is currently treating the hack as an act of espionage, not as an attempt at campaign influence, one source told CBS.