Secret Service agents injured in head-on-collision in New Hampshire that leaves motorist dead

It is unclear whether the agents were part of the security team protecting Hillary Clinton

Police are investigating the circumstances of the accident (AP)

Four on-duty Secret Service officers have been injured in a head-on-collision in New Hampshire that killed the driver of the other vehicle.

It is not clear whether the agents were part of the team escorting Democratic frontrunner Hillary Clinton, who was campaigning on Tuesday night in a nearby town,

New Hampshire police officers said the accident happened at around 7pm in the town of Wakefield. Ms Clinton, the Democratic frontrunner, was holding a town hall meeting in Berlin, north of Wakefield, ahead of voting in the primary contest which takes place in February.

Four agents were injured and the driver of the other vehicle was killed (Twitter)

The Secret Service did not immediately respond to inquiries on Wednesday morning.

The Associated Press said the agents were passengers in a Ford Taurus heading south on a highway, when a northbound Mercury Sable, with three people, crossed over the centre line and collided head-on into the Taurus.

The Sable driver, 45-year-old Bruce Danforth, died at the scene. The AP said the agents suffered serious, but non-life-threatening injuries. The injured passengers were taken to local hospitals.

Police are investigating the circumstances of the accident.