NEW YORK • The explosion hit Chelsea, one of the most fashionable districts of New York, at around 8.30pm on Saturday during a typically bustling time in an area packed with bars, restaurants and luxury apartment blocks.
It came a week after the US financial capital and its 8.4 million residents marked the 15th anniversary of the Sept 11 attacks, and just two days before world leaders led by US President Barack Obama gather in New York for the United Nations General Assembly, a time when parts of Manhattan grind to a halt under draconian security measures.
New York City Mayor Bill de Blasio called the blast on West 23rd Street "an intentional act".
Images of a twisted dumpster in the middle of the street quickly proliferated on Twitter.
The impact shattered windows, damaged cars and sent crowds running from the scene at an hour when Chelsea, always a popular destination, was filled with residents and tourists.
"I heard a big boom," said Mr Luke McConnell, who was visiting from Colorado and had been headed towards a restaurant on West 27th Street. "I felt it, like a concussive wave, heading towards me."
Then came a cloud of white smoke "from the left side of 23rd Street near Sixth", he added.
Witnesses said they could feel the explosion from several blocks away.
Mr Daniel Yount, 34, said he was standing on the roof of a building at 25th Street and the Avenue of the Americas with friends. "We felt the shock waves go through our bodies," he said.
Mr Marcello Begu, 58, was tossing pizzas at a restaurant when he heard the blast. "I've never heard a noise like that in my life," he said. "The ground was shaking. I was scared to go outside."
New York lauds itself as the safest big city in the United States and routinely goes on extra security alert following attacks in other US cities or in Europe.
Violent crime has become rare in Manhattan and stringent security checks have been the norm in many areas since the Sept 11, 2001 Al-Qaeda hijackings that destroyed the Twin Towers. US police claim to have foiled multiple alleged terrorist plots since Sept 11, 2001 when nearly 3,000 people were killed.
AGENCE FRANCE-PRESSE, NYTIMES