An imposter used artificial intelligence to impersonate US Secretary of State Marco Rubio and contact foreign officials, prompting a cybersecurity investigation by the State Department, BBC reports.

According to a leaked State Department cable seen by CBS News, the individual used an AI-generated voice of Rubio to reach out to at least five high-level figures—including three foreign ministers—via the encrypted messaging app Signal.

The cable stated that the person contacted at least five individuals, including the foreign ministers, a US governor and a member of Congress.

The State Department said it is aware of the incident and is taking steps to improve its cybersecurity defences.

The incident was first revealed in the State Department cable that was dated 3 July and sent to "all diplomatic and consular posts," CBS News reported.

The cable stated that a false Signal account was created in mid-June with the display name marco.rubio@state.gov. That account contacted at least five people.

"The actor left voicemails on Signal for at least two targeted individuals, and in one instance, sent a text message inviting the individual to communicate on Signal," the cable stated, as reported by CBS.

The cable did not identify the individuals that were contacted or what the AI-generated voice of Rubio said in those voicemails.

Read full report here.