Police have confirmed on Twitter that 9 people have died and multiple injuries have been reported.
It is now being reported that the crash was a deliberate attack on the market. The driver of the truck has been arrested at the scene and is currently being detained.
The truck ran into the market outside the landmark Kaiser Wilhelm Memorial Church, the Berliner Zeitung newspaper and the Berliner Morgenpost reported.
A photo posted by the Morgenpost showed damaged tables and stalls.
No other details are immediately available about the incident which occurred near the fashionable Kurfuerstendamm avenue in the west of the city.
It is not clear why the truck veered off the road into the market.
Footage on social media appears to show a number of ambulances at the scene.
Minister for Foreign Affairs Charlie Flanagan has said Ireland stands in solidarity with German.
"I am horrified by the loss of life in Berlin this evening. I extend sincere condolences to the families and loved ones of the victims. Our thoughts are also with those injured in this appalling incident.
"I urge Irish citizens in Berlin to follow the advice of local authorities and to make contact with their families who may be concerned at this concern."