Victims sit on the tracks just outside Madrid's Atocha station as they are tended by rescue workers following one of a series of deadly explosions, March 11, 2004.
New York City firefighters walk through the rubble at the World Trade Center, Sept. 11, 2001.
New York City firefighters walk through the rubble at the World Trade Center, Sept. 11, 2001. Corbis
Emergency workers remove a victim after a powerful bomb destroyed two nightclubs in a tourist area on Indonesia's resort island of Bali, in October 2002.
The attacks on London's subway and bus system Thursday bear similarities to last year's commuter-train attacks in Madrid. Spanish prosecutors linked those attacks to al-Qaida. The little-known Secret Group of Al-Qaida's Jihad in Europe claimed responsibility for the London attacks. But that assertion has not been verified.
Following is a timeline of major al-Qaida attacks against Western targets:
Feb. 26, 1993: A massive bomb explodes in a garage below the World Trade Center in New York City. Six people are killed and more than 1,000 injured in the blast. Analysts cite some links to al-Qaida in the attack, though Osama bin Laden disavowed any connection.
June 25, 1996: A powerful truck bomb explodes outside a U.S. military housing complex near Dhahran, Saudi Arabia, killing 19 American servicemen and wounding several hundred people.
Aug. 7, 1998: Two bombs explode within minutes of each other near the U.S. embassies in Nairobi, Kenya, and Dar es Salaam, Tanzania. The blasts kill 264 people.
Oct. 12, 2000: Seventeen American sailors are killed and 39 wounded by a bomb aboard a small boat that targets the the USS Cole, a U.S. Navy destroyer refueling in Aden, Yemen.
Sept. 11, 2001: Hijackers commandeer four commercial jetliners, crashing two of them into the twin towers of the World Trade Center in New York City and another into the Pentagon outside Washington. The fourth airliner crashes in a field in Pennsylvania. Some 3,000 people die in the attacks.
April 11, 2002: A truck carrying natural gas explodes outside a Tunisian synagogue, killing 19 people.
Oct. 12, 2002: A bomb explodes in a resort area on the Indonesian island of Bali, setting off fires and explosions that destroyed two nightclubs. More than 200 people are killed, most of them foreign tourists.
Nov. 28, 2002: Terrorists stage coordinated attacks on Israeli tourists in Mombasa, Kenya. Three suicide bombers crash an explosives-laden sport utility vehicle into an Israeli-owned hotel, killing themselves as well as 10 Kenyans and three Israeli tourists, and wounding dozens of others.
May 16, 2003: Thirty-three people are killed and about 100 others injured in five nearly simultaneous suicide bombing attacks in Casablanca. Twelve of the 14 bombers, all of whom were Moroccan, also die in the attacks.
Nov. 15 & 20, 2003: Car bombs explode within minutes of each other at two Jewish synagogues in Istanbul Nov. 15. A second pair of bombings five days later strike the British consulate and the offices of the London-based HSBC bank in Istanbul. The four bombings kill 58 people and wound about 750.
March 11, 2004: Ten bombs explode within minutes of each other on four crowded commuter trains in the center of Madrid, killing 190 people and wounding more than 1,400.
Timeline by Mary Glendinning; Sources: Facts on File, news reports, GlobalSecurity.org