As concerns about security threats during the upcoming Winter Olympics in Sochi intensify, here is a look at some of the historic attacks and serious threats in Olympic host countries over the decades:

Munich Massacre, Sept. 5, 1972

Munich Massacre

In this Sept. 7, 1972 photo, the West German border police helicopters that carried terrorists and their Israeli Olympian hostages, stand at an air force base west of Munich. (AP)

During the 1972 Summer Olympics in Munich, eight members of the Palestinian Black September terrorist organization broke into the apartment complex where the Israeli Olympic team was staying. Two members of the Israeli team were killed and nine others taken hostage.

The Black September group demanded the release of more than 200 Palestinian prisoners from jails in Israel. The standoff lasted throughout the day before the terrorists and the hostages were taken to an airport by helicopter. A shootout with German police snipers ensued and one of the terrorists eventually detonated a grenade in the helicopter carrying the hostages.

At the end of the shootout and explosion, all nine Israeli hostages were killed, along with five Black September members and one German police officer.

ETA bomb attacks in Spain, 1992

Barcelona Olympics

A tourist looks out at the Olympic Stadium where the 1992 Olympics were held, in Barcelona, Spain, on Wednesday, April 21, 2010. (AP/David Ramos)

The separatist group Basque Fatherland and Freedom, known as ETA, was blamed for several bomb attacks in Spain in 1992, ahead of the Summer Olympics in Barcelona. Shortly before the Games began in July, ETA declared a ceasefire.  

Centennial Park bombing in Atlanta, July 27, 1996

Eric Rudolph

Eric Robert Rudolph is led to a police car by U.S. marshals as he leaves the Jefferson County Jail for a hearing in Birmingham, Ala., in this April 13, 2005, photo. (AP/John Bazemore)

During the 1996 Summer Olympics in Atlanta, a pipe bomb exploded in Atlanta’s Centennial Park, killing one person and wounding more than 100 others in a crowd that had gathered for a concert. Two years later, Eric Rudolph was charged with the bombing. He was also charged with two other bombings that took place after the Olympics and sentenced to life in prison.

Knife attack in Beijing, Aug. 9, 2008

Beijing attack

Tourists stand in front of Beijing's Drum Tower Sunday Aug. 10, 2008, after a relative of the U.S. Olympic Volleyball coach was killed in a knife attack. (AP/Greg Baker)

The father-in-law of one of the players on the U.S. men’s volleyball team was killed in a knife attack in Beijing, not far from the main Olympic stadium during the 2008 Summer Olympics. The man’s wife and tour guide were also injured. The suspect,Tang Yongming, then killed himself. Authorities said he didn’t have ties to any terror groups and may have been mentally ill.