Bad Aibling, Germany: Nine people were killed and more than 100 were injured when two passenger trains collided head-on near a Bavarian spa town about 60 kilometres south-east of Munich on Tuesday.

The collision took place on a single track and one train was derailed, a German police spokesman said.

The cause was unclear and police said that, alongside the rescue effort, investigations were starting into establishing what had happened.

Rescue workers at the scene of the collision in southern Germany. Photo: AP/Josef Reisner

The crash between two local passenger trains happened at 6.48am local time (4.48pm AEDT) near Bad Aibling in the southern state of Bavaria near the border with Austria.

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Dozens of rescue teams were on site and helicopters took some of the casualties to nearby hospitals. The area was sealed off and alongside the rescue effort, a crash investigation had begun, police said.

The trains' operator, Meridian, is part of French passenger transport firm Transdev, which is jointly owned by state-owned bank CDC and water and waste firm Veolia.

Rescue teams prepare to transport an injured person to hospital. Photo: AP

It runs train, tram and bus networks in 19 countries.

Transdev said in a statement that management and staff were terribly shocked by the "exceptionally serious accident" and that Chief Executive Jean-Marc Janaillac was at the scene.

German Transport Minister Alexander Dobrindt, also at the site of the crash, said it was unclear whether it had been due to a technical failure or human error.

Rescue workers retrieve a body at the site where two trains collided head-on near Bad Aibling, southern Germany on Tuesday. Photo: AP

Embassy staff are racing to determine whether any Australians have been affected by the crash, a spokeswoman for the Department of Foreign Affairs and Trade said.

"The Australian Embassy in Berlin is making urgent inquires with local authorities to determine whether any Australians are involved," she said in a statement.

"If you have any concerns for the welfare of family and friends in the region, you should attempt to contact them directly.

"If you are unable to contact them and still hold concerns for their welfare, you can call the Consular Emergency Centre on 1300 555 135 or +61 2 6261 3305."

State-owned Deutsche Bahn is responsible for the track. The line has a system that makes a train brake automatically if it goes through a red light.

Reuters and Rania Spooner