At least 32 people were killed when a tour bus crashed near Taipei on Monday night, with television footage showing the bus careening towards a road barrier before flipping on its side.

Of 44 people on the bus, 30 were pronounced dead at the scene and two died in hospital, the fire department said, adding that 12 people were still being treated in hospitals around Taipei, the capital.

Many of the passengers were elderly, although the age range was early 20s to late 60s, according to city authorities.

The trip had been arranged by the Tieh Lien Hua Travel Agency, according to Taiwan's tourism bureau.

An official with the agency said the tourists were "likely" all from Taiwan, but that it was still looking at passenger information.

"We are making efforts to help with the emergency response and will fully cooperate," Chou Chi-hung told Reuters by telephone.

It was unclear what caused the crash. Local television showed a video of the bus shot from behind flipping onto its side and skidding towards the hillside after it hit a road barrier when negotiating a highway interchange curve.

Ambulances and fire trucks were lined up along the bend of the road as rescue workers used a crane to lift the battered bus from its wheels, after all the passengers were pulled from the wreckage.

"Prosecutors need to get on the site," said cabinet spokesman Hsu Kuo-yung on live TV.

The crash is the latest accident involving tour buses in Taiwan. Earlier this month, another Taiwanese tour bus carrying Chinese tourists crashed into a bridge in southern Taiwan, injuring some passengers.

It followed a grisly murder-suicide last year in which 24 Chinese tourists were killed after the driver set their moving bus on fire.