Former FBI director James Comey was indicted on Tuesday in an investigation over a social media photo of seashells arranged on a beach that officials said constituted a threat against US President Donald Trump, according to a person familiar with the matter.

The person was not authorised to publicly discuss the matter and confirmed the indictment on the condition of anonymity. The charge or charges against Comey were not immediately known.

It is the second criminal case the Justice Department...