Millions of people in the eastern United States awoke to fallen trees, widespread power outages and flooded streets on Tuesday morning after Hurricane Sandy hammered the US East Coast overnight.

The death toll from the storm currently stands at 14, but could rise significantly, rescue workers warn as they begin to assess the widespread destruction.

Five people were reported killed in New York state, including one man who died when he was electrocuted.

Subway and car tunnels have been submerged by floodwaters and power outages have left more than seven and a half million people without electricity, raising concerns the world's financial capital could be crippled for days.

Blazes among floodwaters

New York state officials also reported storm-related fires throughout New York City. In New Jersey, two people were killed when a tree fell onto their car.

Meanwhile, a nuclear power plant just north of Atlantic City is on alert because of rising ocean water. A spokesman for the US Nuclear Regulatory Commission said the Oyster Creek nuclear power reactor declared the alert over fears the flood waters could affect the reactor's service water pumps.

Further casualties were reported in Connecticut and West Virginia. A woman in Canada was reported killed after she was struck by flying debris in Toronto, police said.

Losses run into billions

A US data forecasting company predicated economic losses as a direct result of the storm could reach $20 billion.

US stock markets remained closed for a second day on Tuesday. It is the market's first two-day weather related shut-down since 1888.

Some 14,000 flights have been grounded until Wednesday, according to an airline tracking service.

The disaster has completely overshadowed the US election race, forcing a halt to presidential campaigning a week before Americans head to the polls.

The Florida-based National Hurricane Center said as of 7 a.m. local time (11 a.m. GMT) on Tuesday, the storm had moved westward across Pennsylvania and was centered about 90 miles (144 kilometers) west of Philadelphia. It is expected to move into western New York on Tuesday night and into Canada on Wednesday.

The Center downgraded Sandy to a post-tropical cyclone, with winds reaching up to 150 kilometers per hour (93 miles per hour).

Sandy killed 67 people last week as it battered down on parts of the Caribbean before heading north towards the US Eastern Seaboard.

jlw/ipj (AP, AFP, Reuters, dpa)