Chechen rebels claimed responsibility on Thursday for a small explosion this week near Gazprom's headquarters in southwestern Moscow.
"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 rebel web site Kavkaz Center. "On the contrary: It has come to your homes and your comfortable offices."
A homemade bomb containing three to five kilograms of TNT exploded on Monday on the roof of a garage several hundred meters from the headquarters of Gazprom, the state-controlled gas giant.
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 Gazprom had been targeted to show that the Kremlin had failed to defeat Chechen insurgents.
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 hydroelectric power station in the Kabardino-Balkaria republic, putting it out of action for two years.
Umarov also claimed responsibility for twin suicide bombings that killed 40 people in Moscow's metro in March, as well as the derailment of a Moscow-St. Petersburg train that killed 26 in November.