MOSCOW - Chechen rebels claimed responsibility on Thursday for a small explosion three days ago near the Moscow headquarters of Russia's state-controlled gas giant Gazprom. "The aim of this operation was to show Kremlin businessmen... that the war is not over," Chechen rebel leader Doku Umarov said in a statement posted on the www.kavkazcenter.com Islamist website. "On the contrary: it has come to your homes and your comfortable offices." A home-made bomb containing an estimated 3-5 kilos (6-11 pounds) of TNT exploded on August 9 on the roof of a garage several hundred meters from the headquarters of Gazprom, Russia's biggest company, according to local media. No-one was hurt and the incident had passed largely unnoticed until the rebel claim of responsibility on Thursday. A Gazprom spokesman declined to comment. Umarov said in his statement that Gazprom had been targeted to show that the Kremlin had failed to defeat Chechen insurgents in two wars since the 1991 fall of the Soviet Union. A decade after driving the separatists from power in Chechnya, Russia's leaders are struggling to contain an Islamist insurgency along the country's southern flank. As the self-styled Emir of the Caucasus, 46-year-old Umarov has sought to create a pan-Caucasus state independent from Russia and governed by sharia law, which would include Chechnya and other nearby mainly Muslim provinces in Russia's south. Umarov, Russia's most wanted man, has threatened to attack energy pipelines and power stations as part of an "economic war" on Russia. On July 21, militants stormed and bombed a hydro-electric power station in the Muslim republic of Kabardino-Balkaria, putting it out of action for two years. Umarov also claimed responsibility for twin suicide bombings that killed 40 people on Moscow's metro in March and the derailment of a Moscow-St. Petersburg train that killed 26 in November.