Russian security forces have arrested four men under suspicion of plotting to derail an express train between Moscow and St. Petersburg. The four men were detained last month, Kommersant business daily reported. They were planning to bomb the Sapsan, an express train that runs between the two cities with higher than average ticket prices, as it ran through the countryside near Khimki, a town on the edge of Moscow. They had been under constant surveillance of the Federal Security Service (FSB). On July 18, FSB head Alexander Bortnikov informed Russian President Dmitry Medvedev that a "major act of terrorism" had been prevented, but no further details at that time were provided to the press. The attack would have echoed a bomb blast two years ago that derailed a luxury Moscow-to-St. Petersburg train, killing 26 people. A North Caucasus Islamist group claimed responsibility for the bombing, saying its was carried out on the orders of its leader, Doku Umarov, one of Russia's most wanted rebels.