Barcelona's most famous street was packed with tourists when a van drove into the crowds on a sunny Thursday afternoon, leaving scenes of carnage and panic.
"There were bodies on the ground with people crowding round them. People were crying," Xavi Perez, who sells sports magazines just 100 metres away from the attack, told AFP.
The region's interior minister gave a grim toll from what police said was a terror attack: 13 dead and more than 50 injured.
Among the foreigners caught up on Las Ramblas was Aamar Anwar, a renowned Scottish human rights lawyer in Barcelona for a conference and had been walking down the boulevard when the terror unfolded.
Total panic - we are all getting pushed back- la Ramblas pic.twitter.com/1MwYLfFZJc— Aamer Anwar (@AamerAnwar) August 17, 2017
"All of a sudden I heard a crashing noise and the whole street just started to run screaming," he told Sky News, describing a scene of thousands of people struck by chaos and panic.
"I saw a woman next to me screaming for her kids.
"Literally within 30 seconds, police vans, ambulances, police officers with guns were piling out, and we were sectioned off and then being pushed rapidly back," he said.
Another witness said he saw a man fleeing.
"I saw a man run down the Ramblas, with police chasing him and he appeared to drop a black metal object. It looked like a pistol," said the witness who only gave his first name, Sergio.
Another man at the scene told Spanish television channel TVE that he saw the suspect.
"It was a person in their 20s, he was very young, brown hair, a slim face. I saw him when the van stopped. We were very close to everything."
'Screams and then a crash'
As people ran for their lives they were replaced by armed police officers who sealed off the scene.
"Van upon van of police officers" then arrived, Anwar said. "They have quite clearly unfortunately had to plan for something like this."
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Another visitor, Susan McLean, who was 100 metres away, said it was terrifying.
"All of a sudden, scores of people ran towards us -- hysterical, children hysterical. They first of all said someone had been shot.
"It calmed down for a moment then all of a sudden a second wave of people came down the street. Our hotel was one street away so we got ourselves out," she told Sky.
"We could see the police, we could see all the cars stopped.
"The police were doing their job. We really had no idea what was going on other than we had to get ourselves out of there very quickly."
Tom Gueller, who lives on an adjoining road, fled the scene when he saw the van hurtling through the crowds.
"I heard screams and a bit of a crash and then I just saw the crowd parting and this van going full pelt down the middle of the Ramblas and I immediately knew that it was a terrorist attack or something like that," he told BBC radio.
"I ran away, I mean I live near, I had to run back about 50 metres or so and go up to my flat and obviously see what's happening on the road from my balcony."
Asked about the van, he said: "It wasn't slowing down at all. It was just going straight through the middle of the crowds in the middle of the Ramblas."
Steve Garrett was in a nearby market and sheltered in a bakery with several others.
"Coming from England it was reminding me a great deal of what happened in London, so we were very concerned about what might happen next."
Armed police then appeared.
"They seemed to sweep through the market area. They seemed to be looking for someone. They were going very carefully, very cautiously, stall to stall," he said.
By Daniel Bosque / AFP