The attack in Barcelona is the latest terrorist incident to hit Europe in recent years.
3 June 2017 - London
Eight people were killed when three men drove a van into pedestrians on London Bridge before launching knife attacks on people enjoying a night out in Borough Market.
The terrorists were shot dead by police.
22 May 2017 - Manchester
Suicide bomber Salman Abedi detonated a bomb at Manchester Arena as fans were leaving an Ariana Grande concert, killing himself and 22 others.
7 April 2017 - Stockholm
A stolen truck was rammed into a crowd in the Swedish capital, killing four people and wounding 15 others. A 39-year-old Uzbek man confessed to the crime, his lawyer said.
Police said Rakhmat Akilov was known to have been sympathetic to extremist organisations.
22 March 2017 - London
Khalid Masood drove a hired car over Westminster Bridge, near the Houses of Parliament, mounted the pavement and hit pedestrians before crashing into railings outside the Palace of Westminster.
He stabbed Pc Keith Palmer to death and also killed US tourist Kurt Cochran, Romanian tourist Andreea Cristea, 31, plus Britons Aysha Frade, 44, and 75-year-old Leslie Rhodes. Masood was shot dead by police.
18 March 2017 - Paris
A suspected Islamic extremist attacked a French soldier at Orly airport - shouting that he wanted to kill and die for Allah - and wrested away her assault rifle.
Two colleagues on patrol at the airport shot and killed the man before he could fire the military-grade weapon in the busy terminal.
3 February 2017 - Paris
A machete-wielding man shouting "Allahu akbar" attacked French soldiers guarding the sprawling Louvre museum building. The suspect, who was shot four times, was later named by officials as Egyptian Abdullah Reda Refaie al-Hamahmy, 28.
19 December 2016 - Berlin
A truck ploughed into a crowded Christmas market in central Berlin, killing 12 people and injuring 56 others.
26 July 2016 - Saint-Etienne-du-Rouvray, Normandy
Two attackers killed 85-year-old parish priest Father Jacques Hamel with a blade and seriously wounded another hostage in a church in northern France before being shot dead by French police.
The two hostage-takers had pledged allegiance to Islamic State.
The men arrived as Fr Hamel was leading morning Mass in Saint-Etienne-du-Rouvray, a working-class town near Rouen, north-west of Paris.
24 July 2016 - Ansbach, Bavaria, Germany
A Syrian suicide bomber injured 15 people when he blew himself up outside a music festival.
The suspect, named by officials as 27-year-old failed asylum seeker Mohammad Daleel, 27, had pledged allegiance to Islamic State, had a history of mental illness and faced deportation to Bulgaria.
The terror group claimed responsibility for the attack, saying the bloodshed was carried out by "one of the soldiers of the Islamic State".
22 July 2016 - Munich
An 18-year-old German-Iranian gunman, who was not known to police, opened fire at a crowded shopping centre and fast-food restaurant in Munich, killing nine people and injuring 36, including children.
14 July 2016 - Nice
A truck ploughed into Bastille Day revellers in the southern French city of Nice, killing 86 people. IS claimed responsibility for the attack, which was carried out by a Tunisian living in France.
13 June 2016 - Paris
A police commander and his partner were found dead outside his home in the Paris suburb of Magnanville. The French suspect declared his allegiance to Islamic State leader Abu Bakr al-Baghdadi and threatened to kill non-believers.
22 March 2016 - Brussels
Three IS bombers killed 32 people at Brussels airport and on the capital's subway. The blasts took place during the morning rush-hour.
The bombers were all Belgian.
13 November 2015 - Paris
Suicide bomb-and-gun attacks killed 130 people across Paris, including 89 at the Bataclan music venue. More than 360 people were wounded.
IS said it was behind the attacks.
7-9 January 2015 - Paris
Bloodshed was brought to Paris by gunmen who launched three days of attacks in the capital and surrounding regions. The massacre started with an attack at the offices of satirical magazine Charlie Hebdo, killing 12 people.
It ended with a huge police operation and two sieges. During the bloodshed, another militant killed a policewoman and took hostages at a supermarket, killing four before police shot him dead.