Two commuter trains crashed head-on in southern Germany, killing 10 people and injuring around 90 as they slammed into each other on a curve after an automatic safety braking system apparently failed, the transport minister said.

The regional trains collided before 7am on the single line that runs near Bad Aibling in the German state of Bavaria.

Aerial footage shot by APTN showed that the impact tore the two engines apart, shredded metal train cars and flipped several of them on their sides off the rails.

The first emergency units were on the scene within three minutes of receiving the call, but with a river on one side and a forest on the other, it took hours to reach some of the injured in the wreckage.

Hundreds of rescue crews using helicopters and small boats shuttled injured passengers to the other side of the Mangfall River to waiting ambulances, which took them to hospitals across southern Bavaria.

Nine people were reported dead immediately while a 10th died later in a hospital, police spokesman Stefan Sonntag said - adding that the two train drivers were thought to be among the dead and one person was still missing in the wreckage.

"We have little more than hope of finding them still alive," he said. "This is the biggest accident we have had in years in this region."

German rail operator Deutsche Bahn said safety systems on the stretch had been checked as recently as last week, but Transport Minister Alexander Dobrindt suggested that a system designed to automatically brake trains if they accidentally end up on the same track did not seem to have functioned properly.

Glasgow Times:

Mr Dobrindt, however, said it was too early to draw a definitive conclusion.

"The site is on a curve. We have to assume that the train drivers had no visual contact and hit each other without braking," Mr Dobrindt told reporters in Bad Aibling, adding that speeds of up to 100kph (60 mph) were possible on the stretch.

Black boxes from both trains had been recovered and are now being analysed, which should show what went wrong, Mr Dobrindt said.

"We need to determine immediately whether it was a technical problem or a human mistake," he said.

Authorities had initially reported 150 injured but federal police spokesman Stefan Brandl later lowered that figure to 89. Ten of those had serious injuries, including the person who died in hospital.

Each train can hold up to 1,000 passengers and they are commonly used by children travelling to school. Fewer than 200 people in all were on board on Tuesday, however, because of regional holidays to celebrate Carnival.

"We're lucky that we're on the Carnival holidays, because usually many more people are on these trains," regional police chief Robert Kopp said.

About 700 emergency personnel from Germany and neighbouring Austria were involved in the rescue effort, using about a dozen helicopters.

Glasgow Times:

Train operator Bayerische Oberlandbahn started a hotline for family and friends desperate to check on passengers.

"This is a huge shock. We are doing everything to help the passengers, relatives and employees," said Bernd Rosenbusch, the head of the Bayerische Oberlandbahn.

In Munich, 60km (40 miles) away, the city blood centre put out an urgent call for immediate donations in the wake of the crash.