Death toll rises as killer US storm causes flooding, outages

Seven people have died, some 1.8 million customers remain without power throughout the eastern US and communities on the New England coast face more flooding a day after a powerful storm snapped trees and downed wires.

The remnants of the storm, known as a nor'easter, continued to buffet the northeastern US with wind gusts of up to 80km/h even as it moved hundreds of miles out to sea, hampering efforts to restore power.

The governor of Massachusetts, Charlie Baker, declared a state of emergency on Saturday afternoon, following similar announcements by the governors of Virginia and Maryland on Friday.

The moves give those states access to federal resources. Baker said the National Guard was deployed to numerous municipalities throughout eastern Massachusetts to help with rescue and evacuation efforts.

Trains were running with delays between Washington and New York along Amtrak's Northeast Corridor, the passenger railroad said, after service was suspended for several hours earlier on Saturday due to power outages.

The storm carried hurricane-force winds in excess of 145km/h, sending seawater churning into streets in Boston and nearby shore towns - the second time the area has been flooded this year.

The National Weather Service warned that coastal states from Massachusetts to Maine could experience another round of flooding late on Saturday when the high tide returns, though it is not expected to be as severe as earlier surges.

Falling trees killed seven people, including two boys who died when trees struck their homes, in Connecticut, Maryland, New York, Pennsylvania, Rhode Island and Virginia, according to local media and police.

Private forecasting service AccuWeather said the storm dumped as much as 46cm of snow on parts of New York state and Pennsylvania.

The problems carried over into Saturday, with hundreds of flights cancelled into and out of New York and Boston, according to the website.