HONG KONG: At least five people were killed and dozens more were injured in Hong Kong on Wednesday after a fire broke out in an old residential building in one of the financial hub's most densely populated districts.

Authorities said 41 people were injured and some 300 more were evacuated after the blaze began at the 13-storey building in the city's Yau Ma Tei neighbourhood shortly after 7:53 am (2353 GMT Tuesday).

Hundreds of firefighters put out the fire at the 60-year-old building after several hours rescuing 250 people with 50 more evacuating themselves, Lam Kin-kwan, a local fire department official, told reporters.

Among the injured were 38 hospitalised with burns and inhalation injuries, said assistant chief ambulance officer Tong Sze-ho.

Local broadcasters showed images of some residents waving towels from their windows to appeal for help while others rushed to the building's rooftop.

Lam said the fire started outside a fitness centre on the first floor and quickly began to spread to the upper floor.

Hong Kong leader John Lee said in a statement he was “deeply saddened” by the deaths and injuries and extended his condolences to the affected families.

Hong Kong has some of the world's most densely populated -- and tallest -- apartment blocks.

Deadly fires used to be a regular scourge, especially in poorer neighbourhoods.

But in recent decades safety measures have been ramped up and such fires have become much less commonplace.