Rescuers searched flooded homes for survivors and millions remained without power today as New York city and nearby towns dealt with the aftermath of "superstorm" Sandy.

New York subway trains crawled back to limited service after being shut down since Sunday, but the lower half of Manhattan still lacks power.

Surrounding areas such as Staten Island, the New Jersey shore and the city of Hoboken remain crippled from a record storm surge and flooding.

At least 93 people died as Sandy hit the north-eastern United States on Monday.

Officials said the number could climb as rescuers searched house-by-house through coastal towns.

The financial cost of the storm is set to be very high.

Disaster modelling company Eqecat estimated Sandy caused up to $20bn in insured losses and $50bn in economic losses, double its previous forecast.

At the high end of the range, Sandy would rank as the fourth-costliest US catastrophe ever, according to the Insurance Information Institute, behind Hurricane Katrina in 2005, the 11 September 2001 attacks and Hurricane Andrew in 1992.

The devastation threatened to disrupt next Tuesday’s presidential election, though President Barack Obama, in a tight race with Republican challenger Mitt Romney, appeared to gain politically from his disaster relief performance.

New Jersey Governor Chris Christie, a vocal Romney supporter, praised Mr Obama, and New York city Mayor Michael Bloomberg, a political independent, tonight endorsed Mr Obama.

Some residents may lack electricity for weeks.

New York utility Consolidated Edison restored power to 250,000 customers, leaving another 650,000 in the dark.

The vast majority will be restored by next weekend, but "the remaining customer restorations could take an additional week or more," the company said.

About 4.6m homes and businesses in 15 US states were without power today, down from a record high of nearly 8.5m.

More deaths were recorded overnight in the New York borough of Staten Island, where authorities recovered 17 bodies after the storm lifted whole houses off their foundations.

Among the dead were two boys, aged four and two, who were swept from their mother's arms by the floodwaters, police said.

In all, 38 people died in New York city, officials said.

Sandy started as a late-season hurricane in the Caribbean, where it killed 69 people, before smashing ashore in the United States with 130kmh winds.

It stretched from the Carolinas to Connecticut and was the largest storm by area to hit the United States in decades.

In hard-hit New Jersey, where entire neighbourhoods in ocean-side towns were swallowed by seawater and the Atlantic City boardwalk was destroyed, the death toll doubled to 12.

Floodwaters finally receded from the streets of Hoboken, across the Hudson River from Manhattan, leaving behind a stinky mess of submerged basements and cars littering the sidewalks.

Bruce Springsteen and Jon Bon Jovi, both from New Jersey, will headline a benefit concert for storm victims tomorrow on NBC television, the network announced.

They will be joined by Christina Aguilera, Billy Joel and other stars.

The Federal Emergency Management Agency agreed to cover 100% percent of emergency power and public transportation costs through 9 November for affected areas of New York and New Jersey, up from the traditional share of 75%.

More than 36,000 disaster survivors from New York, New Jersey and Connecticut have applied for federal disaster assistance and more than $3.4m in direct assistance has already been approved, White House spokesman Jay Carney said.

The Pentagon was airlifting power restoration experts and trucks from California to New York to assist millions of people still living in darkness.

Fuel supplies into New York and New Jersey suffered from idle refineries, a closed New York Harbor, damages to import terminals, and a closed oil pipeline.