At least 15 people were killed in the Canadian prairie province of Manitoba on Thursday after a semi-trailer truck hit a small bus that was carrying a group of mainly elderly people, police said.

The crash is one of the most lethal road accidents in recent Canadian history.

The crash occurred at the junction of two major roads near the town of Carberry in southwestern Manitoba, 170 km (105 miles) west of Winnipeg. The bus passengers had been on their way to a casino in Carberry, CBC News reported, citing a casino spokesperson.

"We've been able to establish that at least 15 people have been confirmed deceased as a result of this collision," said Assistant Commissioner Rob Hill, who commands the Manitoba Royal Canadian Mounted Police.

Hill told a televised news conference that "sadly, this is a day in Manitoba and across Canada that will be remembered as one of tragedy and incredible sadness."

The bus had been carrying about 25 people, most of them elderly, he said.

Ten other people were being treated in hospital. Police said the drivers of both vehicles were alive, and declined to say who might have been responsible for the crash.

Media reports initially identified the vehicle as a van rather than a bus. They said it was operated by Handi-Transit, which transports the elderly and those with disabilities.

The Canadian Broadcasting Corporation showed a still photo of a white minivan-sized vehicle that had been burned out. It also showed a picture of a blue truck with a smashed-in front.

Wheelchairs and crumpled walkers remained near tarpaulins covering bodies at the site, the Winnipeg Free Press said.