Transcript for SPECIAL REPORT: At Least 9 Dead When Truck Plows Into Public Square in Berlin

This is an ABC news special work. Now reports. Jaded New York. Good afternoon I'm David Huard ABC news headquarters in new York and we do what it taking pictures at this hour we are monitoring the situation in Berlin that appears to be. Perhaps a terrorist attack of some sort at first they weren't sure whether this was an accident or not. But at this hour police now say they suspected was a deliberate attack. You're looking at pictures coming in from Berlin at this hour showing stalls knocked over were there are reports. From witnesses on the scene of people of lying injured on the ground and here's what we know so far is that. A truck barreled into a crowd it's believed that this was. A Christmas gathering a scene of Christmas shopping in Berlin's main shopping street in the cities of western portion. Of that city and when we heard reports initially. There was concern that this could be. A related to terrorism because of the warnings we are all the where we've been reporting on them for quite some time here by European security services. Following other plots that had been uncovered. Of course over the summer you'll remember. Plot that was carried out and meets the truck that was driven into a scores of victims it was rented a nineteen ton refrigerated truck. That killed so many. We do know at this hour Berlin police now reporting nine people dead several injured and of course the fears. At this early point is that that number could go much higher. As we continue to look at these pictures I want to bring in our senior justice correspondent Pierre Thomas because here you have reported often. About the worries that something like this would be carried out. Exactly. Just a horrific scene playing out. In Berlin as you said nine people killed many more injured. Law enforcement has been warning about potential. Such any type of attack for some months now a November. The State Department issued a alert to warning two Americans traveling abroad in Europe in particular. To be concerned about large gatherings that terrorist attacks could take place again we don't know precisely this was a terrorist attack but that. The feeling. The indicators are pointing toward that at the moment and again even in the US during the Thanksgiving is up Thanksgiving celebration law enforcement officials are. He should generic warnings even though they had no. Specific information of attacks to be on alert at large gatherings and in recent weeks we have the case in Ohio State. Where a man using a vehicle tried to mow down people here inside the united states of David as you said this has been ongoing. Activities. And of course early on as these headlines came in. Early reporting indicated that this could have also been simply an accident a truck. Into a crowd before when police reporting a jump the pavement. And headed into a populated area in the city's western portion where it's believed there's a significant amount of Christmas shopping obviously this time of year. The BBC reporting witnesses describing a quote gruesome scene in that police. Are beginning to evolve and they're thinking they do now suspect this was. Deliberate. Attack though. We await confirmation on that whatever inner chief foreign correspondent Terry Moran and and Terry you've reported on the situation over the summer in peace and as pier as reported here and Brian Ross as well authorities Natalie in this country but around the world have been concerned about. Vehicles being used in these terrorist attacks. Is dated this the latest atrocious method that that these. Terrorist has decided to pick up a news because it's so effective and it's so hard to defend against I have to tell you living in London for many people in the major cities. And elsewhere in Europe it feels. As it's sometimes we are living under siege. These warnings come repeatedly. Especially during the holiday season. In London and other cities. Americans and locals have been warned about going to holiday market to shopping mall to the kinds of places. Frankly that help make the holidays do decked out with festive lights were all kinds of people having a great time. Those are the juicy target for these terrorist and you are absolutely right using trucks. What which are so awful and so deadly and so hard. To guard against a company trucks are on the roads that the driver of the city's. Living in in Europe has become. Psychologically stressful almost at times like living in siege. Terry thank you Brian Ross is standing by our chief investigative correspondent Brian and yeah I should cautioned that it was were watching these pictures come in. That we certainly don't have confirmed reports that this was a deliberate act but as time moves on. It appears more and more likely there are witnesses who reported the truck plowing into this Christmas market. Terry just mention the several warnings the real worries particularly. Within Europe that vehicles can now be used by people trying to make a statement and in this case. There had been heightened alert particularly around the holiday season not only in Europe and as you know Brian right here in the US. Eight happy right Terry iTunes has been calling again and again its followers to use simple means of attack at night. Or a vehicle of some sort now as you recall in the most recent posting they put a picture of the Macy's. Thanksgiving Day parade in New York. On the cover of the warnings and the alerts to their followers. That led to extraordinary precaution in New York during the Thanksgiving Day parade there were no incidents but we do know as fact that. That's iTunes has lost territory and seeing to be suffering that Kiev beat up battle. In Iraq and Syria. They have ramp up their efforts but their followers to attack such soft targets as a Christmas party in Germany are the Bastille day celebration. In Paris and they didn't at least traps so this is a considered sort of a trademark signature attack. By prices nothing fancy nothing spectacular a simple truck rented can cause great damage as which seats in these pictures. And as you reported on here a U mention the Macy's Thanksgiving Day parade there had been some concern certainly stepped up security. In and around New York City to prevent this kind of incident from playing out here and I should just like again caution ever want to sit home and it will certainly we don't have confirmation from Berlin police at this hour. That this was in fact a deliberate attack there had been warnings about this kind of incident happening to our own State Department issuing in late November traveler for all Americans saying that. Basis at al-Qaeda and their affiliates continue to plan terrorist attacks in Europe. With a focus on the upcoming holidays. Season and associated events. Our entire team care Brian Terry we'll continue to work this story and we'll come back on the air if events warrant in the meantime we'll have team coverage coming up tonight. On world news tonight I'm David Miller until it. This has been a special. Or maybe.

This transcript has been automatically generated and may not be 100% accurate.