At least nine people have been seriously injured and many others, including an Australian, have sustained lesser injuries after a tourist bus and a semi-trailer collided in southern Germany.

Most of the more than 30 passengers as well as the bus and the truck drivers were injured in the crash near the city of Heidelberg, police said.

At least 17 people were taken to hospital, including five women and three men from Canada, one woman from Australia, two men from the United States, and three Germans.

As the operator had not provided a complete passenger list it was difficult to give exact numbers, according to police, but they said the group was mainly made up tourists.

The exact circumstances of the incident were unclear, but police said that the bus had driven onto the wrong side of the road.

Five rescue helicopters and seven ambulances were sent to help the injured, while the road was blocked for hours. Both lanes were only reopened late on Thursday night (local time).

German media reported that most passengers were aged 60-plus, and were from the US, Canada and Australia.

It is believed the bus company operates a four-star bus service out of Waghäusel, according to its website, and all buses are equipped with distance regulators and “lane-assisted technology”.

Media reports said about 100 emergency units, including rescue helicopters, rushed to the scene near the small south-western town of Hockenheim (in the Upper Rhine Valley), treating several shocked passengers on the side of the road.

Debris scattered across the road marked where the bus was approaching an on-ramp to the A61 highway on an “L road”, the German equivalent of a secondary road, when the collision happened.

Hockenheim: Schwerer Verkehrsunfall mit Reisebus; mehrere Schwerverletzte pic.twitter.com/Ifkk9xhr1A

— Marco Hanna (@Crash24h) October 11, 2018

Passengers could be seen standing by the side of the road holding back packs and bags as they were helped into waiting ambulances for treatment.

Local Speyer police officer David Faulhaber said “as far as we can see at this moment, the bus moved over to opposite lane and collided with a lorry”.

“Including the lorry driver, we have 35 injured, some of them severely,” Officer Faulhaber told reporters at the crash scene.

A Department of Foreign Affairs and Trade spokesperson said Australian officials were “making urgent enquiries with local authorities to confirm the identity and condition of any Australians involved”, the ABC reported.

-with wires