Hurricane Sandy has battered large parts of the U.S. East Coast, causing chaos across New York City in a freak storm which President Obama described as a 'major disaster'.
The superstorm ripped through the mainland at 6.30pm local time on Monday (11.30GMT), flooding lower Manhattan and leaving half a million people in New York City without power.
After Sandy swept across the eastern coast up from the Caribbean during the day, New York was hit with a 13ft wall of water which caused severe flooding and a power outage to over 7.5million people across the U.S. East Coast.
President Obama declared a major disaster in New York and Long Island, where 911 dispatchers in the city were earlier receiving 20,000 calls per hour due to Superstorm Sandy.
Sandy had earlier been upgraded from a hurricane to a superstorm as it converged with a cold weather system.
New Jersey governor Chris Christie said "the devastation is unthinkable" after surveying aerial images of the area.
The superstorm also caused scares at two nuclear power plants and has bought the presidential election campaigning to an abrupt halt, with President Obama insisting that the first priority is to ensure the safety of those affected.
At least 33 people have so far been reported dead in the U.S. and Canada, including 'at least ten' in New York.
The storm brought gusts of more than 85mph (135kph) and a record-breaking 13ft surge of seawater in Manhattan, submerging seven subway tunnels and many roads.
Mayor Michael Bloomberg said on Tuesday that the damage done to power supplies in the city has been 'unprecedented in scope'.
He said public transport in the city is suspended until further notice, while power could be out in some parts of New York for one or two days.
At Breezy Point in the New York borough of Queens, 190 firefighters are tackling a huge fire that has destroyed more than 50 homes.
New York University hospital was forced to move patients to other hospitals after it lost power and its back-up generator broke down.
Among them were 20 babies from neonatal intensive care - some on respirators operating on battery power.
Firefighters said one man had been killed by a falling tree, while two people were also killed when a tree fell onto a vehicle in New Jersey.
Elsewhere in New Jersey a levee has broken, flooding the towns of Moonachie, Little Ferry and Carlstadt with up to five feet of water.
Some 670,000 New York homes have been left without power by the storm, with electricity knocked out to more than six million Americans.
Related: Superstorm Sandy Yahoo live blog
A total of 15 people have been reported dead by local officials in New York, New Jersey, Maryland, Pennsylvania, Connecticut, West Virginia and North Carolina, while in Toronto, Canadian police said a woman died after being hit by flying debris.
Authorities warned the threat to life and property was "unprecedented" and ordered hundreds of thousands of residents in areas from New England to North Carolina to evacuate their homes and seek shelter.
New York City mayor Michael Bloomberg said the worst of the storm had passed and officials expected the tidal surge to recede by Wednesday.
But thousands of flights have been cancelled at airports in cities up and down the coast, causing widespread travel chaos.
British Airways axed all of its flights to and from New York, Newark, Baltimore, Washington DC, Boston and Philadelphia, and 11 of today's return flights to and from the East Coast have been cancelled.
It had been feared the surge of seawater could damage the underground electrical and communications lines in lower Manhattan that are vital to the nation's financial centre.
The New York Stock Exchange and the Nasdaq suspended trading for a weather event for the first time since Hurricane Gloria in 1985.
Meanwhile Britons caught up in the devastation along the East Coast have spoken of the chaos caused by one of the worst U.S. storms in a generation.
British holidaymaker Tony Lee, who was holed up in an apartment building in Brooklyn overnight, described the ferocity of the storm - which was downgraded from a hurricane to a post-tropical cyclone.
He told Sky News: "There is a lot of bright lights and flashing in the sky. We initially thought we had seen an explosion over the Lower East Side, but locals told us it was probably a transformer that had blown up, so we immediately lost any internet connection, lights and power, so that was quite frightening.
"We were surrounded by green flashes of lightning and this howling wind, and everything bending over and flying at the windows and we are on the fourth floor." He added: "There are things coming off trees and off the roofs, which is frightening."
Television pictures showed a crane on the top of a high-rise building in Manhattan partially collapsed while the facade of a four-storey building in the Chelsea neighbourhood crumbled to the ground.
Footage also showed severe flooding in parts of the city with subways and roads underwater.