Transcript for SPECIAL REPORT: At least 1 dead in Barcelona terror attack

This is an ABC news special group. Good afternoon I'm Tom gum as we continue to follow breaking news out of Europe what is looking more and more like a terror attack. In the heart of Barcelona. Police there tell us a van apparently. Rammed into several people that walking along one of its busiest areas Los Rolf bless essentially this is the Fifth Avenue or slowed up in the heart of the city there. We're being very careful with some with the images we're showing you because there are multiple victims that are laid out all across the floor. At this point right now we understand that Malta people multiple people have died and there are several other victims now one eyewitness telling Spanish media that this. Looked like the van came and speeding off a side street. And just plowed into several people for fifty yards. We plowing over them like porn people went airborne. Our Terry Moran chief for of course one has been monitoring all these developments in Terry this is still an active situation because we understand. The driver and possibly at least one other person are now holed up. In a restaurant. That's right down this is an ongoing fluid attack a terror attack is what Spanish police are now calling the situation. In two phases first the van attacked in this very packed very popular with tourist area of downtown Barcelona and now. What is apparently a hostage situation police sources confirming to ABC news that two gunmen have holed up. In a restaurant nearby apparently a Turkish restaurant near the site of that van attack police are negotiating with them they are telling people. Who are in that district to shelter in place and they are telling people who are not to stay away they are also urging people. Not to share images. Of the carnage there because what is out there right now shows that this has been a very serious attacks I also don't want. To reveal. Two potential attackers their own movements that place is now swarming with police up and down those streets as they secure the area. And they believe they have cornered two gunman now holed up in a restaurant near the site of the van attack. You have a major section of one of the biggest cities in Europe under lockdown right now in a hostage situation. ABC news's will Gretzky a rock to the scene moments after the span attack he joins us now live will would you see. Tom it envoy is normally a very busy part of Barcelona everybody was moving very quickly away from the scene blog. Right near where this attack took place is usually very busy part of this city. Some consider it defender of the city everybody. Was walking very fast some people running our history. Tapas restaurant a long pipe partly de gras yeah that are normally open at this time work closing their doors. Asking people who are heated outside you go inside. And out hotel. Bell men were doing the same actually people who don't siding clear the street. Our will Gretzky who was reporting from Barcelona right now for just join us live we are. Following a terror attack that it's just occurred in Barcelona if these pictures look familiar they are brand new but this attack. Does feel very familiar because Carr attacks then attacks have been happening all across Europe even here in the United States our chief investigative correspondent Brian Ross joins me now why when you look at these pictures when you look at the damage on that Dan and and now be. The situation the hostage situation where that the driver possibly one other man. Our or did hold open a restaurant this looks and sounds very familiar. That's right time there have been no claims of their responsibility and we don't know yet who might be responsible but it has all the trademarks of the attacks we've seen. Inspired by ices ices and sent out word to his followers attacked this way used vehicles use and then you can. Most recently thirteen months ago when a six people were killed in these friends on both Bastille day when a truck ran down. A major highway there since then the Berlin Christmas mark attack and two separate attacks on London bridge and Westminster bridge in London. Told has been huge in these attacks. At least nine or ten major attacks. Said to be inspired by places they continue to send out the word if you can kill anyway you can use of vehicle. Yet we talk about the timing right now it's 656. PM in Barcelona when the attack happened it was 5 o'clock it's an area full of tourist full of people and from what we've heard from eyewitness is this band. Veered off a side street and just plowed into that pedestrian plaza. Exactly and we can see from the pictures we've seen so far there was no indication of any barriers that would prevent him. That's something's not taken place in New York City at Times Square. After a number of these attacks they've begun to put up. Concrete barriers so it's not easy to come off a the year off a side street and rundown of the veterinary elect the wrong us. We do know the president who has been dealing very delicate situations here at home is now dealing with this. International terrorism attack one of another Cynthia Vega who was traveling with the president right now Cecilia. It's how we were told just a few minutes ago that president trump has been briefed were told by the White House that the chief of staff general John Kelly. As aware of the situation and is keeping the president up to speed on everything that is happening. There in Spain there's no word directly from the president himself just yet but the First Lady. In fact is the first one to offer public comments on what's happening there in Barcelona she just tweeted a couple of minutes ago saying. Quote thoughts and prayers to Barcelona. We do know Tom also that there's been a warning from the State Department this afternoon to American travelers. In Spain they are right now Heather Newark the State Department spokeswoman tweeting out that the State Department is closely monitoring events in Barcelona. And that sending a word out to any Americans who are there to stay away. Cecilia Vega for us any time these terror attacks happen abroad and they have happened here in fact we just had a car tax. Over the weekend law enforcement all across the country sit new precautions wanted to Pierre Thomas write and tell us what some of the forties are doing here at home. Tom FB ID HS in New York City officials are monitoring this. Very very closely they typically did NYPD will step up patrols. Have heavily armed units out in public display to deter any kind of potential act of terrorism. Right now law enforcement here has been particularly concerned about these. Low tech type attacks. Every month or so they've been sending out notices to local law enforcement to be. Or on guard to prepare for these kind of attacks. But Tom is a great and growing concern here in the United States and almost impossible to defend a right here thanks so much egregious Joyner coverage we want to update you we are following news of a terror attack in the heart of Barcelona an apparent van attack police there say one person possibly to drove a van at full speed into a pedestrian plaza. Heating several people we know that multiple people have died and several others are injured. And as we've been following these stores for the last two years out of Europe even here at home. These van attacks have been a preferred method of attack. For terrorists across the globe. We're gonna stay on top of this story throughout the afternoon we're have a full update with our entire team. On world news tonight with David Muir we now return to our scheduled program. This has been a special. From ABC.

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