A manhunt is under way after at least 13 people were killed and 100 injured when a van mounted a pavement and ploughed into pedestrians at a popular tourist spot in Barcelona.
Spanish police also shot dead five men wearing suicide belts after they rammed another vehicle into people in Cambrils - nearly 70 miles away.
Here is everything we know about the Spain attacks so far:
- What happened?
At 5pm local time, a white Fiat van was used to ram people in Barcelona's Las Ramblas district, popular with tourists.
The vehicle travelled at speed for more than a third of a mile, striking pedestrians as it went, before it stopped.
Eyewitnesses described scenes of widespread panic, with crowds running in waves away from the area.
Spanish police were quickly on scene and much of Barcelona was soon on lockdown.
Authorities were quick to describe the incident as a terrorist attack.
- A second attack
Hours later five men wearing fake suicide belts used a car to ram people in the Spanish seaside town Cambrils - 68 miles from Barcelona.
Seven people, including a police officer, were injured during the incident early on Friday morning. One victim died later from their injuries.
Bystanders ran for their lives as a gunfire broke out close to the coastal town's beachfront promenade.
Spanish police said they shot dead four of the attackers, while the fifth died later from his injuries.
Pictures from the scene showed an overturned vehicle surrounded by police tape.
- The victims
At least 13 people were killed and 100 injured in Barcelona, with seven people suffering injuries in Cambrils - one who later died in hospital.
Victims in Barcelona include citizens from 34 countries.
A Belgian national is among the dead, Belgium's deputy prime minister Didier Reynders confirmed on Twitter.
France's foreign ministry said that 26 French nationals were injured, including 11 seriously.
Australia has also said that one of its citizens is unaccounted for, while an Irish family were also injured.
- Who is behind the attack?
A manhunt is underway for the driver of the van in Barcelona who is believed to be at large.
Moussa Oukabir, 18, been named as a suspect in Spanish media.
Four individuals are already in custody, Catalan Police have confirmed.
One of the men arrested was Oukabir's older brother Driss.
The Moroccan-born 28-year-old reportedly handed himself into authorities in Spain, but denied involvement in the attack, claiming his younger document stole his documents and used them to hire the van.
Another of the detained individuals is a Spanish national from Melilla.
Catalan regional police said the other two people being detained are also Moroccan-born.
The so-called Islamic State terror group has claimed responsibility for the attack.
Information about the group of attackers in Cambrils is yet to be revealed.
On Friday, police linked an explosion at a house in Alcanar on Wednesday evening to the van attack.
At least one person was killed and six injured when the house blew up, causing substantial devastation to nearby buildings.
Police initially dismissed the incident as a gas explosion.
- What has the response been from world leaders?
Prime Minister Theresa May said she was "sickened by the senseless loss of life in Barcelona" and that "Britain stands with Spain against the evil of terrorism."
In a later media interview she added: "We must work together if we are to confront this evil of terrorism [and] also to confront and deal with the perverted, extremist ideology which drives it."
US President Donald Trump condemned the attack in Barcelona and posted a message on social media saying the US "will do whatever is necessary to help. Be tough & strong, we love you!"
French President Emmanuel Macron tweeted: "All my thoughts and solidarity from France for the victims of the tragic attack in Barcelona. We will remain united and determined."
Belgian Prime Minister Charles Michel also sent a message of support to those caught up in the attack in Spain, tweeting "no barbaric act will undermine the power and resilience of our ally."