At least 13 people have been killed in a fire that has engulfed several high-rise apartment buildings in Hong Kong, authorities say, with some residents reported trapped inside.

Flames took hold in several apartment blocks of the Wang Fuk Court estate in Tai Po, a district in the northern part of the city, on Wednesday afternoon before engulfing other parts of the buildings.

Firefighters battled the blaze into the night as thick, black smoke billowed from the 31-storey towers and orange flames lit up the sky.

Nine people were declared dead at the scene and four sent to hospital were later confirmed dead, said the Fire Services Department, which upgraded the blaze to a level five alarm after nightfall.

At least 15 people were injured, and local media reported that some residents were believed to be trapped inside the buildings.

“There’s nothing that can be done about the property. We can only hope that everyone, no matter old or young, can return safely,” a Tai Po resident surnamed So, 57, told the AFP news agency near the scene of the fire.

“It’s heartbreaking. We’re worried there are people trapped inside.”

Wang Fuk Court is one of many high-rise housing complexes in Hong Kong, a city that is one of the most densely populated areas in the world.

Records show the housing complex consisted of eight blocks with almost 2,000 apartments housing about 4,800 people.