Russian authorities have foiled a plot by militants who were building fertilizer bombs in a suburban apartment and planning to attack a bullet train between Moscow and St. Petersburg, a newspaper reported on Monday. Citing security sources, Kommersant revealed details of an alleged plot by militants from the North Caucasus that Russia’s top security official had described to President Dmitry Medvedev last month as a “large terrorist attack” targeting transport. Militant leader Doku Umarov has vowed more bombings in Russia’s heartland. A deadly attack would be a blow to Medvedev and Prime Minister Vladimir Putin ahead of a March 2012 vote in which one of them is expected to run for president. Kommersant said the suspected mastermind, a 22-year-old native of the North Caucasus province of Kabardino-Balkaria, allegedly recruited at least three other men to help carry out the attack on the Sapsan, a high-speed train connecting Russia’s largest cities.