Authorities said firefighters were called in soon after thick smoke belched from the 23rd floor flat in Kwai Ching House at around 4.35 am.
A dog and a cat were also found lifeless in the public housing unit.
Firefighters said there was a certain amount of clutter in the unit, which hindered the operation to some degree.
A spokesman said the fire was largely put out at 5.15 am. Officials have yet to ascertain what had caused it.
Around 30 residents in the building were evacuated by firefighters, while 200 others left on their own.