Previous incidents include:
1972: Eleven Israeli athletes and officials died after terrorists from the Black September faction of the Palestine Liberation Organisation struck at the Munich Olympics. Two wrestlers were shot in the athletes' village and the others died after a botched ambush by German police. Five of the eight Palestinians and one German officer were also killed.
1996: The Olympics was again the target for terror - this time in Atlanta. Two people died and 111 were injured after pipe bombs in a rucksack exploded in the Centennial Olympic Park. Eric Rudolph, an anti-abortion extremist, was jailed for life in 2003 after pleading guilty to the bombing.
2008: A suicide bomber killed 15 people including a government minister when he targeted the start of a marathon race near Colombo in Sri Lanka. The bomb killed 15 people, including a number of runners, and injured 90 others. The Sri Lankan government claimed the militant group Tamil Tigers were responsible for the attack.
2009: Six Sri Lanka cricketers were wounded, and six policemen and two civilians killed, after an attack by Islamic extremists in Lahore, Pakistan. The terrorists set off explosives and sprayed the team bus with bullets after staging an ambush - an outlawed militant groups with close links to Al-Qaida is believed to have organised the attack.
2010: Three people died after rebels in Angola attacked the Togo national football team's bus. The assistant coach, another official and the bus driver died, while two players were among nine people injured in the attack as the team headed to African Nations Cup.