(CNN) -- 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.Resonance from the attacks was immediately felt in other urban centers, with New York police announcing a hike in security levels on the city's subway system in direct response to the events in Moscow.Read more: Female suicide bombers blamed for attacksBut say experts, while many heightened security measures are in place on metro systems in major cities, little can be done to prevent future attacks without disrupting the infrastructures of the world's urban powerhouses.Even as Russian authorities beefed up security on their already well-monitored transport network, officials conceded they would be powerless to halt determined suicide attackers from committing further atrocities."The subway is a vulnerable system, you can never protect it 100 percent," Konstantin Kosachev, internal affairs committee chairman of the Russian State Duma, told CNN. "It is absolutely unpredictable."The fact no watertight security solutions have been developed in the wake of numerous attacks highlights the dangers that continue to hang over transport networks -- risks only exacerbated by their claustrophobic confines."