MADRID (REUTERS, AFP, BLOOMBERG) - Spanish authorities believe there may have been eight people involved in a cell which carried out an attack in Barcelona on Thursday (Aug 17), and that the group had planned to use butane gas canisters, a judicial source with knowledge of the investigation said on Friday.

Catalan government official Joaquim Forn also told local radio earlier on Friday that it was possible that attackers had meant to use canisters in the attack on Thursday in which a suspect drove a van at speed along a busy pedestrian street.

Meanwhile Catalan emergency services said the death toll in the Barcelona attack as well as a separate attack in Cambrils, a town south of Barcelona, rose to 14 on Friday when a woman injured in Cambrils died.

Security forces are hunting for the van's driver, who was seen escaping on foot, and police said they had killed five attackers on Friday night in Cambrils to thwart the attack there.

Six civilians and a police officer were injured in the second incident, which the government said was connected to the Barcelona attack. Also on Thursday, a person was killed in an explosion in a house about 100km south-west of Barcelona, in an incident linked to the attack, police added.

"The priority right now is work out the identity of these people, to prove and show the relationship between the different people involved, those that took the van and those that have been able to escape," Forn said.

The suspects broke through a checkpoint early Friday and began running over pedestrians on the oceanfront promenade, after which they were shot by police, La Vanguardia newspaper said. They wore explosive belts, the report said.

Spanish region's head Carles Puigdemont later told local radio station RAC1 that the belts were fake.

The driver of the van in the Barcelona attack, who drove the rented vehicle at a speed of about 50 miles (80 km) down the avenue, ploughing into pedestrians, is still at large.

The attack bore all the hallmarks of similar recent atrocities in Berlin, Nice, London and Stockholm. In addition to the victims, at least 100 people were injured. Islamic State in Iraq and Syria (ISIS) said it was responsible, according to the SITE Intelligence Group.

FOUR SUSPECTS ARRESTED

Police said on Friday they have arrested four men over the twin attacks. They said the fourth arrest was made in Ripoll - the same city in northern Catalonia where another suspect and Driss Oukabir, a Moroccan, have already been detained on suspicion of as-yet unspecified involvement in the attacks.

Police are searching for Driss Oukabir's brother Moussa, but it was not known whether he was the latest person arrested.

It was still not clear how many attackers had been involved.

Witnesses said the white van zigzagged at high speed down Las Ramblas, a busy avenue thronged with tourists, knocking down pedestrians and leaving bodies strewn across the ground.

ISIS' Amaq news agency said: "The perpetrators of the Barcelona attack are soldiers of the Islamic State and carried out the operation in response to calls for targeting coalition states" - a reference to a US-led coalition against the Sunni militant group.

The claim could not be immediately verified.

If the involvement of Islamist militants is confirmed, it would be the latest in a string of attacks in the past 13 months in which they have used vehicles to bring carnage to the streets of European cities.

That modus operandi - crude, deadly and very hard to prevent - has killed well over 100 people in Nice, Berlin, London and Stockholm.

"We're united in grief," Spanish Prime Minister Mariano Rajoy said in a televised address after rushing to Barcelona, the biggest city in Catalonia, a region in Spain's north-east whose separatist government is defying Madrid.

"Above all we're united in the firm intention to defeat those who want to take our values and way of life from us."

AT LEAST 34 NATIONALITIES AMONG VICTIMS

There were at least 34 nationalities among the victims, Spain's civil protection agency said on Friday.

The agency tweeted that among the dead and injured in Barcelona, a city hugely popular with tourists worldwide, and the seaside resort of Cambrils were nationals from France, Pakistan, Spain, the Netherlands, China, Venezuela, Mauritania, Australia and Britain.

Belgium said one of its citizens died in the Las Ramblas assault, while The Hague said three Dutch were injured and a Greek diplomat reported three nationals had been wounded - a woman and her two children.

The French foreign ministry said 26 French citizens were injured in the attack, of whom 11 are in serious condition. French Foreign Affairs Minister Jean-Yves Le Drian said he will visit Barcelona on Friday.

A spokesman for the German Foreign Ministry said on Friday that he thought 13 German citizens were among those injured. Martin Schaefer told reporters that some of the Germans had been injured very seriously. He said he could neither confirm nor rule out at this point that Germans were among the dead.

British tourist Keith Welling, who arrived in Barcelona on Wednesday with his wife and nine-year-old daughter, said they saw the van drive past them down the avenue and took refuge in a restaurant when panic broke out and the crowd started running.

"People were shouting and we heard a bang and someone cried that it was a gunshot... Me and my family ran into the restaurant along with around 40 other people.

"At first people were going crazy in there, lots of people crying, including a little girl around three years old."

It was the deadliest attack in Spain since March 2004, when Islamist militants placed bombs on commuter trains in Madrid, killing 191 people and wounding more than 1,800.

The Spanish royal household said on Twitter: "They are murderers, nothing more than criminals who are not going to terrorise us. All of Spain is Barcelona. Las Ramblas will go back to being everyone's."

World leaders have condemned the violence, expressing outrage and solidarity with the victims.

US President Donald Trump said: "The United States condemns the terror attack in Barcelona, Spain, and will do whatever is necessary to help." He added: "Be tough & strong, we love you!"

Britain's Prime Minister Theresa May said she was "sickened by the senseless loss of life in Barcelona", and added that the foreign office was working to establish if any British nationals were involved in the incident.

Canadian Prime Minister Justin Trudeau also condemned the terrorist attack, saying: "Canada will continue working with the international community to fight terrorism and build a world where we can all feel safe and secure."

Speaking to the media on Friday morning, Australian Foreign Minister Julie Bishop said Australia "stands with" the people of Barcelona in the wake of the attack, in which three Australians were also injured.

"The Australian government condemns this brutal and deliberate act clearly designed to harm tourists on holiday in Spain," Ms Bishop told the press.

She said that one Australian woman, believed to be from New South Wales, is in hospital in a serious but stable condition, while two young men said they were affected, but they had gone back to their hotel and would seek medical assistance in the morning.

BODIES ON THE GROUND

Catalan police said the two men detained on Thursday had been arrested in two towns, Ripoll and Alcanar, both in the region of Catalonia, of which Barcelona is the capital.

The explosion was also in the town of Alcanar, in the early hours of Thursday. One person died and another was injured in that incident, police said.

Mobile phone footage showed several bodies strewn along the Ramblas, some motionless. Paramedics and bystanders bent over them, treating them and trying to comfort those still conscious.

Around them, the boulevard was deserted, covered in rubbish and abandoned objects, including hats, flip-flops, bags and a pram.

Regional head Carles Puigdemont said people had been flocking to hospitals in Barcelona to give blood.

Holidaymaker Ellen Vercamm told El Pais newspaper: "We saw a white van collide with people. We saw people going flying."

A witness named Rebecca told La Vanguardia: "I've seen a lot of people knocked down on the floor and the people are running and crying. The van drove down the middle of the street dragging everyone with it."

TOURIST DRAW

The incident took place at the height of the tourist season in Barcelona, which is one of Europe's top travel destinations with at least 11 million visitors a year.

French President Emmanuel Macron, whose nation has suffered some of Europe's deadliest militant attacks in recent years, tweeted: "All my thoughts and France's solidarity to the victims of the tragic attack in Barcelona."

A Vatican spokesman said Pope Francis was praying for the victims and wanted to express his closeness to all Spanish people, especially the victims and their families.

The authorities in Vic, a small town outside Barcelona, said a van had been found there in connection with the attack. Spanish media had earlier reported that a second van had been hired as a getaway vehicle.

Following the attack, security staff at Barcelona airport suspended a strike that started in early August. "Our work is now more necessary than ever," a spokesman said.