Hong Kong leader John Lee said another 279 people were reported missing. He said 29 people remained in hospital.
Some 700 people have been evacuated to temporary shelters after the blaze broke out at the Wang Fuk Court housing complex in the city’s Tai Po district.
The dead included one firefighter, officials said earlier.
Video from the scene showed at least five buildings close to each other were ablaze.
A number of firefighters were said to have been hurt while trying to tackle the flames as they ripped through the 31-storey towers.
Records show the Wang Fuk Court site consisted of eight blocks with almost 2,000 apartments housing around 4,800 residents, including many elderly people.
The fire, which broke out at 2.51pm local time, had spread on bamboo scaffolding set up around the exterior of the complex, reports said.
Renovation work was being carried out at the site, according to local media.
Firefighters have been seen aiming water at the intense flames from high up on ladder appliances.
Pictures showed thick grey smoke billowing out from the buildings as emergency services battled to control the blaze.
Flames and smoke were still shooting out of many windows as night fell.
Tai Po is in the northern part of Hong Kong and close to the border with the mainland Chinese city of Shenzhen.
Bamboo scaffolding is a common sight in Hong Kong at building construction and renovation projects.
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However, the government said earlier this year it would start phasing it out for public projects because of safety concerns.
Wang Fuk Court is a complex under the government’s subsidised home ownership scheme.
It has been occupied since 1983, according to the property’s website.
