[cnn-photo-caption image=http://i2.cdn.turner.com/cnn/2009/WORLD/asiapcf/01/22/pakistan.militant.arrest/art.bus.afp.gi.jpg caption="The aftermath of London's subway and bus bombings of 2005."]
The deadly rush hour carnage which hit Moscow's subway on Monday highlights a potential danger that millions of people around the world are exposed to on a daily basis as they enter transport networks, say security experts.
Suicide bombers have been blamed for the bombings at two stations on the same underground rail line, with separatists from Russia's Chechnya region, linked to previous transport system attacks, claiming responsibility.
While authorities say it is too early to confirm who is behind the latest outrage to target Moscow, it matches a modus operandi previously employed not only by Chechen rebels, but other groups worldwide, usually to potent deadly effect.
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