Russian city hit by suicide bombing for second straight day For the second time in as many days, an explosion rocked the Russian city of Volgograd Monday morning. Russian officials say a suicide bomber blew himself up on a trolleybus, killing at least 14 people and wounding nearly 30 others. The latest attack came one day after at least 17 people died in a suicide bombing at the city's central rail station. The explosion ripped away much of the bus's exterior and broke windows in nearby buildings. The BBC reported that the explosion took place near a market in the city's Dzerzhinsky district. It virtually paralyzed public transport in the city, forcing many residents to walk long distances to get to work. Volgograd, a city of 1 million people formerly known as Stalingrad during the Soviet era, is located approximately 425 miles due northeast of the Black Sea resort town of Sochi, site of next February's winter Olympics. Both cities are located near the unstable North Caucasus region, where Islamic insurgents have waged a campaign of violence against rule from Moscow for the better part of two decades. The latest attacks will undoubtedly heighten fears by Russian officials that militant groups could step up the violence with the attention of much of the world expected to be on Sochi for the Olympic Games. In a statement to Reuters, an IOC spokeswoman said. Our condolences go to all those affected by today's bombing in Volgograd. Unfortunately, terrorism is a global phenomenon and no region is exempt, which is why security at the Games is a top priority for the IOC. At the Olympics, security is the responsibility of the local authorities, and we have no doubt that the Russian authorities will be up to the task. Russian Olympic Committee chief Alexander Zhukov said Monday there was no need to take any extra steps to secure Sochi in the wake of the Volgograd bombings, as "everything necessary already has been done." Russian authorities have introduced some of the most extensive identity checks and sweeping security measures ever seen at an international sports event. Anyone wanting to attend the games that open on February 7 will have to buy a ticket online from the organizers and obtain a "spectator pass" for access. Doing so will require providing passport details and contacts that will allow the authorities to screen all visitors and check their identities upon arrival. The security zone created around Sochi stretches approximately 60 miles along the Black Sea coast and up to 25 miles inland. Russian forces include special troops to patrol the forested mountains flanking the resort, drones to keep constant watch over Olympic facilities and speed boats to patrol the coast. The security plan includes a ban on cars from outside the zone from a month before the games begin until a month after they end. Suicide bombings have rocked Russia for years, but most have been in the North Caucasus region. However, Volgograd has now been struck three times in two months -- suggesting militants may be using the transportation hub as a renewed way of showing their reach outside their restive region. Russian authorities have been slow to introduce stringent security checks on bus routes, making them the transport of choice for terrorists in the region. A few months ago authorities introduced a requirement for intercity bus passengers to produce ID when buying tickets, like rail or air passengers, but procedures have remained lax. No group has claimed responsibility for either explosion, which occurred several months after Chechen rebel leader Doku Umarov called for new attacks against civilian targets in Russia, including the Sochi Games. Umarov had ordered a halt to attacks on civilian targets during the mass street protests against President Vladimir Putin in the winter of 2011-12. Umarov previously claimed responsibility for twin bombings on the Moscow subway in March 2010 by female suicide bombers that killed 40 people and wounded more than 120, as well as a suicide bombing in January 2011 at Moscow's Domodedovo Airport that killed 37 people and injured more than 180. Putin had ordered security stepped up at railway stations and airports around Russia after Sunday's bombing, which occurred during a period when many Russians travel to celebrate the New Year with their families. Putin on Monday summoned the chief of the main KGB successor agency and the Interior Minister to discuss the situation, and sent the former to Volgograd to oversee the probe.