An overnight fire tore through a building in the southern Taiwanese city of Kaohsiung on Thursday, killing 46 people and injuring dozens of others in the island's deadliest blaze in decades.

The fire broke out in the 13-storey, mixed-use building in the small hours of Thursday morning, according to officials, raging through multiple floors before firefighters finally got it under control.

Pictures published by Taiwan's official Central News Agency showed smoke billowing out of the building's windows as firefighters desperately tried to douse the flames using extendable hoses.

Kaohsiung's fire department said it sent more than 70 trucks to tackle the blaze, which took four hours to put out.

As daylight broke, the sheer scale of the fire became clear, with every floor of the building visibly blackened and most of its windows shattered.

The fire department said the blaze "caused 41 injuries and 46 deaths", with officials adding that most of the fatalities occurred on floors seven to 11, which housed residential apartments.

The first five floors were for commercial use but were unoccupied.

Residents reported hearing a number of loud noises when the fire first broke out on the lower floors.

"I heard many loud bangs - 'bang, bang, bang' - on the ground floor and came down to investigate," an unidentified man who lived in the building told Formosa TV.

"That's when I realised there was a fire and called the police," he added.

An unnamed female survivor, describing the scene on her floor, said: "When I opened the door to get out, the hallway was full of black smoke."

As night fell on Thursday, police announced emergency services had finished searching the building with no further casualties found.

Rescue operations. Photo: STR, CNA, AFP

A constable at the Kaohsiung police department told AFP the building was 40 years old and mostly occupied by low-income residents.

Survivors had estimated about 100 people lived in the apartment block, the constable added, giving only his surname Liu.

Officials had not yet ruled out arson, he added.

The fire looks set to be Taiwan's deadliest in years. The last fire of a similar magnitude was in 1995, when 64 people perished inside a packed karaoke club.

Photo: AFP

As an island frequently battered by earthquakes and typhoons, Taiwan has strict building codes and a generally good safety record.

But there is often a gap between what the rules state and how safety standards are applied, especially in older buildings.

Some of the highest death tolls in recent earthquakes have come when older buildings have collapsed, with subsequent investigations occasionally showing their designs were not up to code.

Earlier this year 49 people were killed when a train hit a truck that had slid onto the tracks, in the island's worst railway disaster in decades.

Subsequent investigations revealed government agencies had ignored repeated warnings that such an accident was possible on that particular stretch of mountainside track.