At least 13 people have died and 50 have been injured after a van ploughed into a crowd of pedestrians in the popular tourist area of Las Ramblas in Barcelona, police and local officials say.
There were also reports two armed men entered a restaurant and took hostages, but the interior ministry denied this.
Catalan police have confirmed they are treating the incident as a terrorist attack, with Interior Minister Joaquim Forn adding the number of fatalities will likely rise.
Witnesses have described a scene of chaos and panic as the vehicle zigzagged along the pedestrian area, mowing down people and sending others fleeing for cover.
Ethan Spidey, 25, told The Independent there was a “stampede” as tourists and locals sprinted away from the scene of the attack.
“I was with my boyfriend just about to cross Las Ramblas and all of a sudden there was an immediate stampede and police shouting at people to run,” he said.
“I saw a young child knocked over and picked them up but everyone was just running.”
“There was a stampede in the streets alongside Las Ramblas as everyone tried to run away. People were running into shops and taking refuge in cafes. There was a lot of screaming."
One witness told Sky News: "It was quite terrifying. All of a sudden scores of people ran towards us, hysterical, children hysterical... first of all they said someone had been shot.”
She added: "We really had no idea what was going on other than that we needed to get ourselves out of there very quickly... there was just hundreds of people running away very quickly."
Another said: "We were just told to run, it must have been quite close because... there was an immediate stampede to run away. We were just a minute away from it."
Police have identified Driss Oukabir as the man who allegedly rented the van used in the incident. It’s unclear if he was involved in the attack.
ISIS has claimed responsibility for the attack via its Amaq agency.
More as we get it.