An Australian woman who was sitting metres from where a truck ploughed into a crowded Christmas market in Berlin has described the devastation, saying there was "blood and bodies everywhere".

Trisha O'Neill had been celebrating the last day of her German classes for the year at a Christmas market in Kurfürstendamm when the truck came careering through the stalls.

"We sat just behind the stall having a gluhwein and then all of a sudden there was a big boom and the people in front me jumped on top of me," she said.

"I just saw this huge black truck speeding through the markets crushing so many people and then all the lights went out and everything was destroyed.

"I could hear screaming and then we all froze. Then suddenly people started to move and lift all the wreckage off people, trying to help whoever was there."

Ms O'Neill said they waited there because they had no idea what would happen next.

They were afraid to see the people lying on the ground.

"Eventually we had to and there was blood and bodies everywhere," Ms O'Neill.

"People, including children and older people, weren't moving — people were crying and I just burst into tears.

"All the police and ambulance came and we decided to walk away from the streets and go somewhere safe."

Sorry, this video has expired Truck runs into crowded market in Berlin

Ms O'Neill and her friends fled to a nearby apartment near Nollendorfplatz where they sat in shock, grappling with what had just happened.

Soon they began calling their family and friends to let them know they were safe.

Originally from Brisbane, Ms O'Neill has been living in Germany since September.

The 24-year-old had travelled to Germany on a one-year visa, hoping to gain work in the country.

"I never thought I would see something like this in my life," she said.

"I'm shaking and scared. It all just happened so fast."