At least 19 people died, including nine children, and dozens were injured when a fire tore through a high-rise apartment building in New York City on Sunday, its mayor said, in one of America's worst residential fires in recent memory.

"We know that we have 19 people who are confirmed dead, as well as several others in critical condition," Mayor Eric Adams told CNN, adding that 63 people had been wounded.

"This is going to be one of the worst fires in our history," he said.

"Join me in praying for those we lost, especially the 9 innocent young lives that were cut short," he added in a later tweet.

At least 200 firefighters responded to the blaze, which broke out just before 11:00 am (1600 GMT) on the second and third floors of a 19-story building on East 181st Street, several blocks west of the Bronx Zoo.

Neighbors spoke of seeing residents desperately waving from floors, apparently trapped and unable to escape.

"It was chaos," George King, who lives directly adjacent the building told AFP.

"I've been here 15 years and it's the first time I've seen something like this.

"I saw the smoke, a lot of people were panicking. You could see that no one wanted to jump from the building. People were waving from the windows," he added.

The injured were taken to five hospitals; many suffered from cardiac and respiratory arrest and severe smoke inhalation, officials said.

There were fears of a growing toll.

New York City Fire Department Commissioner Daniel Nigro said that flames quickly engulfed much of the structure and that the smoke was so dense as to be "unprecedented."

He said "very heavy" fire and smoke "extended the entire height of the building."

"Members found victims on every floor, in stairwells," Nigro told reporters.

"The last time we had a loss of life that may be this horrific was a fire which was over 30 years ago, also here in the Bronx," he added.

Photographs and video posted on social media showed flames and thick black smoke billowing out of a third-story window of the brick building as firefighters operated on a nearby ladder.

The cause of the fire was not immediately clear but fire marshals were investigating, said Nigro.

He explained that the fire originated in a duplex apartment on the second and third floors of the building.

'Horrific'

The door to the apartment had been left open, allowing the fire and smoke to spread, Nigro said.

"If you close the door the smoke and fire spread is contained within that apartment instead of spreading up the stairs," he told reporters.

Buildings like this one don't have fire escapes, he added.

Adams said the fire was "truly a tragedy," adding that many residents had been displaced.

"This is really a horrific day for us," he said.

Nigro said the fire was the worst since a blaze at Happy Land nightclub in 1990 in the Bronx, which killed 87 people.

In December 2017, 13 people were killed in a blaze in an apartment building in the Bronx in New York City's deadliest fire in 25 years.

Sunday's inferno comes just four days after a fire in Philadelphia killed 12 people, including eight children, in a three-story public housing building.