A series of underground gas blasts in Taiwan's southern city of Kaohsiung have killed 24 people and injured 271 others.

The explosions sparked a huge fire that tore through the city's Chian-Chen district and were powerful enough to upturn cars and split open paved roads.

One of the blasts left a large trench running down the centre of a road, edged with piles of concrete slabs torn apart by the force of the blast. Residents described the blasts as feeling like a powerful earthquake had hit the area.

"The explosions were like thunder and the road in front of my shop ripped open. It felt like an earthquake" Taiwan's Central News Agency quoted an eyewitness as saying.

"I saw fire soaring up to possibly 20 storeys high after a blast and fire engines and cars being blown away while around 10 bodies lay on the street" another witness told AFP.

The National Fire Agency said four firefighters, who were at the scene investigating gas leaks at the time of the explosions, were among those killed.

It said the local fire department received calls of gas leaks late on Thursday and then there was a series of blasts around midnight affecting "an area of two to three square kilometres".

The blasts were believed to have been caused by a leak of propene, a petrochemical material not intended for public use, but the source of the gas was not immediately clear, officials said.

Kaohsiung Mayor Chen Chu said several petrochemical companies have pipelines built along the sewage system in the area.

"Our priority is to save people now. We ask citizens living along the pipelines to evacuate" he told TVBS television.

Xinhua news agency described smoke with a "gas-like smell" seen coming out of drains in the streets before the explosions. Reports said hospital emergency rooms in the city were packed with casualties.

Officials urged people to stay out of the district and people were using schools to take shelter.

Power was also cut off in some areas, making it difficult for rescuers to search for people who might be buried in rubble. The explosions come just a week after a TransAsia Airways plane crashed in Taiwan during bad weather, killing 48 people.

This man witnessed the explosions: