New York (AFP) - New York is reassuring tourists that America's biggest city is safe as it prepares to welcome more than five million visitors for the busy holiday season after the Paris attacks.

The winter tourism season officially kicked off with Thursday's Thanksgiving Parade, where hundreds of thousands of people lined the streets to watch the three-hour event amid tight security.

After the Paris attacks on November 13, an Islamic State group propaganda video broadcast images of New York from Times Square. US authorities hit back that there was no credible threat against the city or anywhere else in the United States.

"We had some hotel cancellations from small groups," said Chris Heywood, senior vice president of global communications at NYC and Company -- the city's official marketing and tourism organization.

Despite what he calls a "sprinkling of a few cancellations," he is still encouraging people to visit the metropolis for the "magical holiday season" that lasts through December until New Year.

"The city is open," he told AFP. "It is business as usual."

Eighty-nine people were killed at the Bataclan concert hall in the Paris attacks, but the Broadway League says there has been no drop in attendance since the carnage in France.

The US State Department has issued a worldwide travel alert, warning Americans of a heightened terrorist threat in "multiple regions," which has added to the worry among tourist industry professionals.

"We have seen a fall in reservations," said the chief executive of Air France, Alexandre de Juniac, during a visit last week to New York, the prime target in the September 11, 2001 attacks on the US.

A US airline also said reservations from Europe were down, without wanting to give figures.

"I was in a plane 90 percent empty," Christine Priotto, mayor of Dieulefit, a town in southern France, told AFP after arriving this week in New York on a private visit.

"It was a little strange."

- 'People don't want to come' -

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In Times Square, where police armed with heavy guns can be seen patrolling, bus ticket tout Farid Et Takaouy said he had never seen so little trade for the end of November.

"It's really dropped over the last two weeks," he said. "People take photos of the police and send them to their friends everywhere and so people don't want to come any more," he told AFP.

He says people who dress up as Mickey Mouse, Buzz Lightyear and as Statues of Liberty to pose with tourists in exchange for a few dollars have also seen their business fall.

Tourism is a hugely important industry in New York City: an influx of 5.3 million people was expected for the holiday season, which authorities say brings $3.7 billion to the local economy.

On Wednesday, the famous Rockefeller Center Christmas tree will be lit. The open-air skating rinks are open, the famous department stores have already got their Christmas windows decorated.

But some tourists are still thinking twice, particularly those from France.

Alexandra, a French woman from Aix-en-Provence, planned a trip to New York with her husband and their two teenagers long ago. But the Paris attacks and the IS group's propaganda video dampened their enthusiasm.

"In all the emotion, we questioned whether we should travel and at the moment our son doesn't want to go," she told AFP, not wanting to give her second name.

The family are thinking about it. Reassured by the stepped-up security, Alexandra thinks in the end they will still visit New York.

"We are more aware," said the mayor Priotto. But she says she has been more touched by the welcome from New Yorkers than the police patrols.

"When I went to the Statue of Liberty, one man, a ticket seller, took me into his arms," she said, still surprised. "And another said, 'Vive La France.'"