Photo: The Canadian Press

UPDATE: 4:25 p.m.

Thursday van attack in Barcelona has injured 100 people, authorities say.

Victims were left sprawled in the street, spattered with blood or crippled by broken limbs. Others fled in panic, screaming or carrying young children in their arms.

"It was clearly a terror attack, intended to kill as many people as possible," Josep Lluis Trapero, senior police official, told a news conference late Thursday.

The Islamic State group claimed responsibility, saying in a statement on its Aamaq news agency that the attack was carried out by "soldiers of the Islamic State" in response to the extremist group's calls for followers to target countries participating in the coalition trying to drive it from Syria and Iraq.

After the afternoon attack, Las Ramblas went into lockdown. Swarms of police brandishing hand guns and automatic weapons launched a manhunt in the downtown district, ordering stores and cafes and public transport to shut down.

Several hours later authorities reported two arrests, one a Spanish national from Melilla, a Spanish-run Mediterranean seafront enclave in North Africa, and the other a Moroccan.

But Trapero said neither of them was the van's driver. The arrests took place in the northern Catalan town of Ripoll and in Alcanar, the site of a gas explosion at a house on Wednesday night. Police said they were investigating a possible link to Thursday's attack.

UPDATE: 12:15 p.m.

A white van jumped up onto a sidewalk and sped down a pedestrian zone Thursday in Barcelona's historic Las Ramblas district, swerving from side to side as it plowed into tourists and residents. Police said 13 people were killed and more than 50 wounded in what they called a terror attack.

The afternoon attack left victims sprawled out in the street, spattered with blood or crippled by broken limbs. Others fled in panic, screaming or carrying young children in their arms. As witnesses and emergency workers tried to help the wounded, police brandishing hand guns launched a search of side streets looking for suspects.

Police immediately cordoned off the city's broad avenue and ordered stores and nearby Metro and train stations to close. They asked people to stay away from the area so as not to get in the way of emergency services. A helicopter hovered over the scene.

A few hours later, Catalan police tweeted: "We have arrested one man and we are treating him as a terrorist." They said no suspects were holed up in a Barcelona bar, as local media had reported, and began to evacuate stores on the sprawling avenue where scores of people had taken cover.

State-owned broadcaster RTVE reported that investigators think two vans were used — one for the attack and a second as a getaway vehicle.

UPDATE: 11:40 a.m.

A regional government official in Spain says 13 people have been killed in the van attack at a historic shopping and tourist area of Barcelona.

Catalan Interior Minister official Joaquim Forn also said on Twitter that more than 50 people were injured during Thursday's attack.

Regional police now are evacuating stores and bars in the Las Ramblas district amid a manhunt after the attack.

The move came right after police announced they had arrested one suspect and were "treating him as a terrorist."

ORIGINAL: 9:45 a.m.

A white van jumped the sidewalk Thursday in Barcelona's historic Las Ramblas district, killing and injuring several people as it plowed into a summer crowd of tourists and residents, police said. The El Pais newspaper said police were treating the crash as a terror attack.

Police cordoned off the broad, popular street, ordering stores and nearby Metro and train stations to close. They asked people to stay away from the area so as not to get in the way of emergency services. A helicopter hovered over the scene.

Quoting unnamed police sources, El Pais said the two perpetrators of the crash were holed up in a bar in Tallers Street. There was no immediate police confirmation of the report.

Catalan police tweeted that "there are mortal victims and injured from the crash" without specifying numbers. The Barcelona-based La Vanguardia newspaper reported at least one dead and 20 injured from the van.

In a photograph on public broadcaster RTVE, three people were lying on the ground in the street of the northern Spanish city Thursday afternoon, apparently being helped by police and others. Other videos showed five people down and recorded people screaming as they fled the scene.

Las Ramblas, a street of stalls and shops that cuts through the centre of Barcelona, is one of the city's top tourist destinations. People walk down a wide, pedestrian path in the centre of the street but cars can travel on either side.

Keith Fleming, an American who lives in Barcelona, was watching TV in his building just off Las Ramblas when he heard a noise and went out to his balcony.

"I saw women and children just running and they looked terrified," he said.

He said police are there with their guns drawn and riot police are at the end of his block. He said his street is now deserted.