At least 13 people have died and more than 100 have been injured after a van ploughed into pedestrians in a terror attack in a busy tourist area of Barcelona.

Spanish police arrested two people after a white Fiat van tore through the Las Ramblas district which was packed with shoppers and holidaymakers.

The vehicle careered into terrified pedestrians in the busy tree-lined promenade, one of the most popular parts of the city.

Following the van attack, police had reportedly been searching for a man named Driss Oukabir after the passport of a Spanish citizen, of Moroccan origin, was found at the scene.

But El Pais newspaper said Oukabir had denied being involved in the attack and told police that his documents had been stolen.

The identity of those arrested is not clear.

Police patrol the scene of the terror attack caused by the white vanPolice patrol the scene of the terror attack caused by the white van (Manu Fernandez/AP)

There were also reports that detectives believe two vans were used, one for the attack and a second as a getaway vehicle.

Unconfirmed local reports suggested an attacker had been shot by police on the outskirts of the city.

Police also said a driver had run over two police officers in a town north of the city, but it was not clear if this was related to the attack.

The Islamic State terror group has claimed responsibility.

Where the attack took place in BarcelonaWhere the attack took place in Barcelona (PA Graphics)

Lawyer and University of Glasgow rector Aamer Anwar was walking in Las Ramblas when he heard screaming.

He said a shopkeeper told him five or six people were badly injured and described the scene as “chaos”.

Mr Anwar old the Press Association: “I had been to the Cathedral and was walking down Las Ramblas for something to eat.

“Part of it was in the shade so I decided to keep walking down and literally within 10 seconds there was a crashing noise.

“I turned around and people were screaming. I could see a woman screaming with her kids. People started running and jumping into shops.

Children, some in tears, are escorted down a road in BarcelonaChildren, some in tears, are escorted down a road in Barcelona (AP Photo/Manu Fernandez)

“I ran for about 50 or 100 metres and stopped to see what was happening.

“The police were very quickly on the scene and getting people to move back.

“I could see chaos right at the top area and I spoke to a shopkeeper who had run down and was screaming.

“He was Bengali so I spoke to him in Urdu and he said a van had driven into a crowd and he thought there were five to six people very seriously injured.”

Steve Garrett was in a nearby market and sheltered in a bakery with several others after streams of people ran inside.

Police officers tell members of the public to leave the scene in a street in BarcelonaPolice officers tell members of the public to leave the scene in a street in Barcelona (AP Photo/Manu Fernandez)

One member of the group who took refuge with him said she had heard gunshots after the incident.

Mr Garrett told the BBC: “A very large number of people ran into the market area in a big kind of way, lots of screaming, lots of shouting.

“The security guards immediately responded. We ran into the bakery with four or five other people and ran straight upstairs and hunkered down whilst an enormous wave of people went through the market.

“The lady that was with us said she heard some gunshots.”

Emergency service workers at the scene in Las RamblasEmergency service workers at the scene in Las Ramblas (Vil_Music/PA)

Mr Garrett said a “second wave” of people then entered the market, followed by armed police.

He said: “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.”

The terror attack – the deadliest on Spanish soil since more than 190 people died in the Madrid train bombs in 2004 – brought widespread condemnation.

Carles Puigdemont, the president of Catalonia, confirmed the two arrests at a press conference.

He also said 12 people were confirmed dead and at least 80 taken to hospital, which conflicted with interior minister Joaquim Forn, who said 13 people had died.

A Belgian national is among the dead, Belgium’s deputy prime minister Didier Reynders confirmed on Twitter.

Catalonian police said 15 people were seriously injured in the attack.

The Government of Catalonia said Mr Puigdemont had declared three days of mourning for the region.

Barcelona attackPeople running away from Las Ramblas (Giannis Papanikos/AP/Press Association Images)

The two suspects in custody are a Spanish national from Melilla and a Moroccan but neither were the van driver, Catalan authorities said.

Officials are also linking the van attack to an explosion in Catalonia the previous day in which one person was killed.

In another incident, police said a driver had run over two officers in a town north of Barcelona, but it was not clear if the incident was related to the van attack

Local media reports said a white Ford Focus ran over the officers and that a person from the car was shot and killed by officers.