More than 160 firefighters have responded to the blaze in New York which reportedly started on the fourth floor of the building.
Local media is reporting that 15 people have been taken from the building with serious injuries.
At least one child has been confirmed among those killed in the fire.
New York Mayor Bill de Blasio’s press secretary confirmed six of the deaths earlier and said he expected the number to rise.
He tweeted: “Will be more. Horrible. Fire Commissioner on scene. Mayor here shortly.”
The blaze engulfed the five-storey building on Prospect Avenue in Belmont.
The fire began at around 11.50pm GMT (6.50pm local time).
More to follow…