London, Paris, Berlin, Brussels - Europe's big cities are increasingly on high alert for terror attacks.
LONDON - March 22, 2017: Two people are dead and many are injured when a car mounts the footpath on Westminster Bridge before a man stabs a police officer with a knife at Westminster Palace.
PARIS - February/March 2017: Soldiers managed to stop an attempted attack at Paris Orly airport by shooting a man who tried to take a patrolling soldier's gun. In early February, a soldier on patrol shot an Egyptian assailant wielding a machete.
BERLIN - December 2016: Germany's capital was the scene of an attack which killed 12 people when a supporter of Islamic State steered a truck into a crowded Christmas market. The suspect, a 24-year-old Tunisian man, was shot by police near Milan a few days later.
NICE, FRANCE - July 2016: At least 86 people died when an attacker drove a truck into the crowded beach-front Promenade des Anglais. Islamic State claimed responsibility for the attack.
BRUSSELS - March 2016: Islamist attackers set off several bombs at the airport of the Belgian capital and in a metro station, killing 32 people.
ISTANBUL - January 2016: An Islamic State suicide attacker killed 12 Germans when they blew themselves up in the middle of a tourist group near the Hagia Sophia and the Blue Mosque.
PARIS - November 2015: In a coordinated series of attacks on the Stade de France football stadium, several restaurants and the Bataclan music venue, Islamic State supporters killed 130 people and injured hundreds more.
COPENHAGEN - February 2015: A 22-year-old opened fire on a cafe in the Danish capital, killing one person. He then shot and killed a man guarding a synagogue before being shot himself by police.
PARIS - January 2015: Seventeen people died in an attack on the offices of Charlie Hebdo magazine and a kosher supermarket. Both attackers were later killed by police. Terror organisation Al-Qaeda in the Arabian Peninsula (AQAP) claimed responsibility.
BRUSSELS - May 2014: A French Islamist was arrested after shooting four people in the Jewish Museum of Belgium. The gunman was a self-proclaimed jihadist and had previously fought in Syria.
LONDON - July 2005: Four British Muslims set off bombs on the London Underground rail system and on a bus. The attacks killed 56 people and injured around 700.
MADRID - March 2004: Around 191 people died and 1500 were injured when coordinated bombs went off on Spanish commuter trains.
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