WASHIGTON: At least six people have died and up to two million were left without electricity after powerful storms hit the US Atlantic coast.

The storms swept across West Virginia, Virginia, Washington and Maryland, with wind speeds of up to 120 km per hour.

At least six people were killed in the storms, while over four million homes and businesses, 1.3 million in Washington area alone, were left powerless. Virginia and West Virginia have declared states of emergency.

The dead included two in Virginia, two in New Jersey, one in Maryland and one in Washington DC.

The storms left behind felled trees, streets littered with fallen branches and downed power lines.

The storm is locally referred to as a "derecho”, which means a violent windstorm associated with a fast-moving band of severe thunderstorms.

The power cuts left many without air conditioning after a day of record-breaking 40 degrees Celsius heat.

The Washington metro lines were affected, with trains sent to their end points after trees fell across the tracks and power was lost.