A day after superstorm Sandy blasted the U.S. East Coast, at least 40 people have been killed, millions along the East Coast have been left without power and transport across the north-eastern U.S. has been severely disrupted.

Photo taken on Oct. 29, 2012 shows vehicles in a flooded street in Queens Borough of New York, the United States. Sandy, the 10th hurricane this year, was considered one of the strongest storms ever to affect the U.S. east coast. [Wang Chengyun/Xinhua]

The storm that made landfall in New Jersey on Monday evening with hurricane force cut power to at least 7.4 million across the East, according to news report.

New York was among the hardest hit, with 18 people killed, its financial centre closed for a second day and seawater cascading into the still-gaping construction pit at the World Trade Center. The storm also caused the worst damage to the city's subway system in history, and there was no indication of when the largest US transit system would be rolling again.

The death toll from Sandy in the U.S. included several killed by falling trees. Sandy also killed 69 people in the Caribbean before making its way up the Eastern Seaboard.

Airlines canceled more than 12,000 flights. New York City's three major airports remained closed.

The U.S. Department of Energy said that at least eight million homes and businesses have been left without power.

In New Jersey, where the superstorm came ashore, a huge swell of water swept over the small town of Moonachie, and authorities struggled to rescue about 800 people, some living in a trailer park. Police and fire officials used boats to try to reach them.

"I saw trees not just knocked down but ripped right out of the ground. I watched a tree crush a guy's house like a wet sponge," mobile home park resident Juan Allen said.

The massive storm reached well into the Midwest with heavy rain and snow. Chicago officials warned residents to stay away from the Lake Michigan shore as the city prepared for winds of up to 96 kph and waves exceeding 7.2 meters well into today.

President Barack Obama declared a major disaster in New York and Long Island, making federal funding available to residents. He suspended campaigning again yesterday.

"This was a devastating storm, maybe the worst that we have ever experienced," New York City Mayor Michael Bloomberg said.

But he added at a news conference late in the day: "The good news is we're on the road to recovery.''

In New Jersey, Gov. Chris Christie described devastation including seaside rail lines washed away and parts of the coast still underwater.

"It is beyond anything I thought I'd ever see," he said. "It is a devastating sight right now."