Spectators packed Manhattan sidewalks on Thursday to watch the marching bands, floats and giant balloons of Macy's annual Thanksgiving Day Parade, held under tight security two weeks after deadly attacks in Paris.

New York officials said about 3.5 million spectators would turn out for the city's signature parade, now in its 89th year. They urged residents and visitors to carry on with holiday plans, saying there were no credible threats to the most populous U.S. city.

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Police walked alongside many of the parade groups and helicopters hovered overhead amid the enhanced security following the Nov. 13 attacks in Paris. Islamic State militants have claimed responsibility for the assault in which 130 people died.

"We live in a society of being fearful," said spectator Jacqueline Williams, 52, of Atlanta, who was viewing the parade for the first time. "But it's almost like you can't be, because whatever's going to happen is going to happen; you can't stop it."

About 50 million people worldwide were expected to watch the televised parade that snakes through 2.5 miles of Manhattan. The show ushers in both the U.S. holiday season and the busiest time of year to travel.

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A Reuters-Ipsos poll shows Americans have become more concerned about threats since the Paris attacks and identified terrorism as the most important problem facing the country.