The bus, carrying 46 passengers, crashed through a concrete barrier on the side of the road and fell 30 metres (yards) into a ravine in southern Tainan County, according to cable TV station TVBS.

"The driver said that the brakes failed," an emergency official said. "The road there is very narrow, but we still don't know the exact cause of the accident."

The passengers were members of a parents' association from a elementary school in southern Kaohsiung and were on an outing when the accident happened, the official said, adding that it was unclear how many children were among the dead and injured.

TVBS had earlier reported four children had been killed.

All the injured had been taken to neighbouring hospitals, the official said.

Television footage showed the crushed wreckage of the green bus astride a small creek at the bottom of the steep ravine.