Image caption New Jersey bore the brunt of the storm, which hit the US coast on Monday night

President Barack Obama resumed the election campaign suspended in the aftermath of storm Sandy, which wreaked havoc in the north-eastern US.

Mr Obama visited storm-hit New Jersey on Wednesday, while Republican rival Mitt Romney has been holding rallies after restarting his own campaign.

Meanwhile New York's first subway trains set off since Monday, when the network closed for the storm.

Sandy left more than 80 dead in the US, causing havoc on the east coast.

New York Mayor Mike Bloomberg announced in a Thursday press conference that the death toll in that city now stood at 37.

Sandy cut power from millions of homes and paralysed transport.

The storm made landfall on Monday night in New Jersey, where some 20,000 people remain trapped in their homes by sewage-contaminated floodwater.

The president might have spent another day above the fray, but he is heading out west, where it seems his team think supporters may need a little personal encouragement to vote

In New York City, the storm brought a record tidal surge that swamped the subway system and caused widespread blackouts.

Earlier, it killed nearly 70 people in the Caribbean and caused extensive crop destruction in impoverished Haiti.

Severe congestion

New York has begun a slow recovery from the storm.

Subway trains started running again at around 05:30 (09:30 GMT) on Thursday, but services were limited and there were no trains in lower Manhattan.

The New York Times reported that some trains were relatively empty.

Many bus services are already back on the roads, and most of the city's bridges have reopened.

But the newspaper said that on Wednesday there was severe congestion in the streets, and buses were extremely slow and crowded. TV footage showed similar scenes on Thursday.

Police are refusing access to Manhattan to vehicles carrying fewer than three people.

New York State governor Andrew Cuomo has announced that all fares on commuter trains, subways and buses will be waived on Thursday and Friday, in the hope of relieving traffic jams.

As the city struggled to return to normal, people were seen gathering round power strips in the street to recharge their mobile phones and filling up buckets of water at fire hydrants.

The New York Stock Exchange reopened on generator power after two days of closure, along with the Nasdaq exchange.

But New York City's Bellevue Hospital had to order the evacuation of some 500 patients after back-up electricity failed.

The Holland Tunnel, connecting New Jersey and New York City, remains flooded.

Flights resumed at JFK and Newark Liberty airports on Wednesday. The city's LaGuardia airport reopened on Thursday. Nearly 20,000 flights were grounded by Sandy.

'Long haul'

Mr Obama has planned campaign stops on Thursday in Nevada, Colorado and Wisconsin.

On Wednesday, he toured parts of New Jersey struck by the storm with Republican Governor Chris Christie.

Media playback is unsupported on your device Media caption President Obama pledged help for those affected by Sandy as he visited Brigantine, New Jersey

"You guys are in my thoughts and prayers," the president said during a visit to an emergency shelter in Atlantic City. "We are going to be here for the long haul."

More than five million homes and businesses across the north-east still have no electricity. Some utilities are warning it could take seven to 10 days to restore full power.

In the New Jersey city of Hoboken, across the Hudson River from New York City, the National Guard has arrived to evacuate about 20,000 people and distribute meals.

Gov Christie, usually one of Mr Obama's fiercest critics, spoke of his "great working relationship" with the Democratic president.

"I cannot thank the president enough for his personal concern and compassion for the people of our state," said Mr Christie.

Mr Romney held two rallies in Florida on Wednesday, where his campaign said he tried to strike a "positive tone".

Election day is on 6 November, and polls suggest the candidates are running neck and neck.

Eight out of ten voters in a Washington Post/ABC poll gave Mr Obama an "excellent" or "good" rating for his handling of the emergency.

The BBC will be providing full online live results of the US presidential election on 6 November. More details here.