A busy tourist thoroughfare in the heart of Barcelona became a scene of carnage Thursday when terrorists plowed a van through the pedestrian mall and killed at least 13 people.

ISIS claimed responsibility for the rampage, which also injured dozens of pedestrians as the white van mounted a sidewalk on Las Ramblas street at around 5 p.m. and zigzagged into the crowds for blocks.

Bloodied bodies were left sprawled on the street — including an elderly couple lying hand-in-hand — while terrified vacationers ran for their lives.

“We saw a white van collide with people. We saw people going flying because of the collision, we also saw three cyclists go flying,” witness Ellen Vercamm told Spanish newspaper El Pais.

Two people were arrested over the attack, although neither was the driver, who ran off after crashing the van into a newsstand halfway down the street, police said.

The attack sent onlookers scrambling for cover in stores as police locked down the popular shopping district, where just minutes earlier tourists and locals were happily strolling the tree-lined strip in the summer sun.

“Chaos broke out. We heard screaming and then a stampede,” Gary Ritkes, a tourist visiting from Florida, told a local ABC affiliate.

Ritkes and his wife almost lost one of their four kids in the chaos, but the whole family found refuge in a pastry shop, where they lay on the floor in terrified silence with more than 40 others.

Through the windows, they could see police scouring the area for the attackers, others still fleeing the carnage — and bodies being hauled away, he said.

“Everyone was in panic mode, basically fearing for their lives,” Ritkes told Local 10.

Marc Esparcia, a 20-year-old student who lives in Barcelona, told the BBC that he hid in a Starbucks.

“There was a loud noise, and everybody ran for cover. There were a lot of people, lots of families. This is one of the most visited sites in Barcelona,” he said.

“It was horrible. There was panic. Terrible.”

One survivor said she was hunkered down in a Zara clothing store for more than two hours before police let her out.

“Everyone was screaming and running. We had to run up to the roof and throw our bags over a wall. We were all together along this wall, and we were scared we were going to have to jump,” Tamara Jurgen, a Dutch visitor, told The Associated Press.

Despite the panic, photos and videos showed good Samaritans trying to help those injured in the attack.

In one photo, an elderly couple is seen lying in a pool of blood, their hands clasped together as people try to revive the man.

A later image showed the man’s body covered with a sheet.

One of the two men arrested Thursday was identified as Driss Oukabir, 28, whose name was reportedly used to rent the van.

But Oukabir, a native of Morocco, said he was innocent.