German authorities are investigating how two commuter trains fitted with automatic braking systems collided head on in southern Germany, leaving at least ten dead and scores injured.

Key points: Ten dead, scores injured as trains collide

Ten dead, scores injured as trains collide Hundreds involved in rescue operation

Hundreds involved in rescue operation Investigation ongoing to determine whether technical or human error

One of the trains sliced into the other, ripping its side apart and causing several carriages to overturn in the crash near Bad Aibling, about 60 kilometres south-east of Munich.

Teams were sent to the scene after the crash happened at 6:48am (local time) on Tuesday, and helicopters and ambulances took the injured to hospital.

Rescue teams are still searching for one missing person in the mangled wreckage.

Police said 10 people were killed, while 18 were seriously hurt and 63 had minor injuries.

The two train drivers and a conductor were among the dead, local broadcaster Bayerische Rundfunk reported.

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Hundreds of firefighters, emergency services workers and police officers were deployed in the rescue operation, which is complicated because the forest crash site was difficult to access.

German Transport Minister Alexander Dobrindt said the rail track was fitted with an automatic braking system aimed at preventing such crashes, and that investigators were probing if there had been "a technical problem or human error".

"One train was jammed into the other and the carriage of the second train was completely torn apart," he said.

Three black boxes on the trains should help shed light on the accident, he said, adding that two had already been recovered, and the third should be found soon.

The trains collided at high speed on a single track, and the drivers probably did not see each other until the last minute because the crash happened at a curve, Mr Dobrindt said.

"At the moment we will have to wait (for the result of the investigation)," he said.

"Everything else is speculation, and would be unhelpful and inappropriate."

'Enormous shock' for Germany

Emergency services stand next to the crashed train near Bad Aibling in south-west Germany. ( Reuters: Michael Dalder )

Local media have reported it was likely there were fewer people on the train than usual due this week's Fasching or Carnival celebrations in parts of southern Germany.

"I am dismayed and saddened by the serious train accident this morning at Bad Aibling," German Chancellor Angela Merkel said in a statement.

"The accident is an enormous shock for us," said Bernd Rosenbusch, who heads the Bavarian rail company BOB that operates trains on the route.

"We will do everything to help travellers, their relatives and our employees."

Christian Schreyer, chief executive of Transdev, said: "We are deeply shocked and stunned that something like this could have happened. Our thoughts are with the victims and relatives of the victims".

The accident is believed to be the first deadly train crash since April 2012, when three people were killed and 13 injured in a collision between two regional trains in the western German town of Offenbach.

The country's deadliest post-war accident happened in 1998, when a high-speed ICE train linking Munich and Hamburg derailed, killing 101 people and injuring 88 in the northern town of Eschede.

ABC/Wires

