Man shot dead by police on New Hampshire-Maine bridge

A man connected to a homicide in New Hampshire has been shot dead by police on a bridge that connects the US state to Maine.

An eight-year-old child was found shot to death in the man's car, the attorney-general's office said Thursday.

The Piscataqua River bridge connects Portsmouth, New Hampshire, to Kittery, Maine.

The incident started with a man killing a woman at a home overnight in Troy, New Hampshire, about 160km away in the western part of the state, and then driving to the bridge, Attorney-General John Formella said in a news release.

"Early this morning police engaged with the adult male on the bridge in an incident that ended with the male being fatally shot. The Maine Attorney-General's office is now investigating that officer-involved shooting incident," it said.

"Police on the bridge also found an eight-year-old child fatally shot. The exact circumstances surrounding this incident remain under active investigation."

There was no threat to the public and the bridge remained closed because of the investigation, the release said.

No names have been released.