German Chancellor Angela Merkel described the attack on the Christmas market in central Berlin as a terrorist attack.
"I invited the ministers and directors of the special services to hold consultations on the progress of the investigation and the possible consequences."
Previously, Berlin police described this attack as deliberate. A truck driver ran over a crowd gathered at a Christmas market in the German capital on Monday night.
As a result of the attack, at least 12 people were killed and 48 wounded. The attacker, a 23-year-old Pakistani who is already detained, would have entered Germany with the wave of refugees by the end of 2015, following the so-called Balkan route.
His possible co-driver, a Polish national, was found dead in the vehicle and could be a victim of the attack. Berlin police suspect the truck, a Polish-registered Scania, was stolen at a construction site in Poland.