A US government employee has been arrested for threatening to kill President Donald Trump, and using his work computer to research the alleged plot, prosecutors said.

Investigators allege Dean DelleChiaie, 35, who is employed as a Federal Aviation Administration (FAA) contractor in New Hampshire, searched the internet for how to get a gun into a federal facility, and the phrase "I am going to kill Donald John Trump".

There have been three other prosecutions for threats against Trump in the past week, including one where former FBI director James Comey was charged over an Instagram photo of seashells.

The accused is due to appear in court on Tuesday. His lawyer could not be immediately reached.

Dean DelleChiaie, a mechanical engineer for the department that oversees US airspace, is also accused of having searched for details about the families of Vice- President JD Vance and Defence Secretary Pete Hegseth, prosecutors said.