A bus packed with elderly Christian worshippers struck a roadside barrier and overturned in Hong Kong, killing 12 people and injuring 49 others, officials said on Thursday.

The bus, with seats for 55, was carrying around 65 passengers at the time of the accident, police said.

TV pictures showed rescuers pulling victims out of the wreck through a small gap in the roof with the collapsed upper half of the bus wedged against a high roadside barrier in Sai Kung, Kowloon.

"The bus has been seriously damaged; the roof has been badly crushed which pressed down on the passengers inside making it very difficult for emergency services and firemen to carry out our rescue work," said Ho Chak-kan, an acting police superintendent of Traffic in Kowloon East.

The driver, who was injured, was also charged by police with dangerous driving. The cause of the accident is still under investigation.