The fire originated from the third floor of a five-floor building in New York City's Bronx borough.
Authorities said firefighters rescued 12 people from the building.
NY Fire Commissioner Daniel Nigro told a news conference that those killed ranged in age from one to 50 and added that "people died on various floors of the apartment".
The cause of the fire is not yet known.
Another four people were "fighting for their lives" following the fire, the city's fire department said on Twitter.
Firefighters try to rescue people trapped in the NY fire.
L'alerte orange levée dans les Pyrénées — Avalanches
Quant à la Savoie, des avalanches sont prévues sur les routes d'altitude et avec un risque de quatre sur cinq. L'événement, en cours, doit se terminer au plus tôt dimanche à 7 heures du matin.
More than 160 firefighters helped bring the blaze under control.
Calling it "one of the most exceedingly bad misfortunes of life in numerous, numerous years", New York City Mayor Bill de Blasio said that another four individuals who were basically harmed in the burst were "battling for their lives".
An apartment fire in New York, US which killed at least 12 people, including a one-year-old child, has been described as "historic in its magnitude" by city officials.
"I know there were concerns raised about the building itself", Mr de Blasio told WNYC.
"The hunt of the building proceeds with so we realize that despite the fact that it's appalling to report 12 are dead as of now, we may lose others too", the leader said. He also thanked the NYC fire department and and first responders for their quick action and bravery, as well as the medical staff at Jacobi Medical Center helping those in critical condition. The Red Cross handed out blankets to those on the street, as some residents fled the building without shoes or coats.
Some tenants of the building climbed down fire escapes, but the flames moved so fast that many never made it out of their apartments.
Jobs And Workforce Increase In Metro Dalton
The job growth came in the private service-related industries such as trade, transportation, and warehousing. The growth rate outpaced the state's job growth rate of 1.9-percent and the nation's 1.4-percent rate.
The fire broke out around 6:51pm (2351 GMT) in a 25-apartment building near the Bronx Zoo, one of the most popular tourist attractions in the USA financial capital.
Nigro said: "Our hearts go out to every person who lost a loved one here and everyone who is fighting for their lives".
"It is the time of year where people celebrate and certainly here we have people who have lost their lives, lost their homes, lost everything and we grieve with them as everyone in this city should and does".
"The smoke was insane, people screaming, 'Get out!,'" a witness, Jamal Flicker, told the New York Post.
The Associated Press said the fire was the deadliest in NY - excluding the 9/11 attacks - since 87 people died at a social club in the Bronx in 1990.
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Trump said he thought a prolonged probe "makes the country look bad" but said it has energized his core supporters. When pressed on the issue, Trump replied, "It doesn't bother because I hope that he's going to be fair".