A Chechen rebel group notorious for its high-profile terrorist attacks, including hostage-takings at a Moscow theater and a Beslan school, said Friday that its members blew up Russia’s biggest hydroelectricity plant earlier in the week.

Officials were quick to cast doubt on the announcement, which coincided with Prime Minister Vladimir Putin’s arrival at the Sayano-Shushenskaya hydroelectric plant with a group of ministers Friday.

The group, which calls itself Riyadus Salikhiin, said in a statement posted on the rebel web site Kavkaz Center that Chechen rebels decided earlier this year to step up an “economic war” against Russia and sent several sabotage groups into the Russian regions.

The groups were supposed to disrupt the work of the oil and gas pipelines, electric power stations and industrial enterprises, the statement said.

The statement said Monday’s accident at the Sayano-Shushenskaya hydroelectric plant, in which more than 60 people died, was caused by an anti-tank grenade with a timer, installed in the plant’s turbine room.

The rebels pledged to continue similar attacks, arguing that the “anxiety of the infidels’ leadership demonstrated that this operation delivered them a big blow.”

The group was created in 2002, when then-rebel leader Shamil Basayev claimed that it included potential suicide fighters to carry out the high-profile terrorist attacks. The letter posted Friday also claimed responsibility for a suicide car bombing of a police station in Nazran on Monday, which killed 25 people and wounded more than 200.

The Kremlin on Friday shrugged off the Chechen rebel claims as “idiotic.”

“We are not going to comment on idiotic claims,” a Kremlin source told Reuters, without elaborating further.

Investigative Committee spokesman Vladimir Markin said nothing indicated there was a terrorist attack directed against the power plant.

“The FSB’s specialists have not found traces of explosives at the site of the accident,” he said, Interfax reported.

A spokesman for the Federal Security Service contacted by The Moscow Times on Friday afternoon declined comment.

Energy Minister Sergei Shmatko ruled out terrorism as a possible cause of the dam accident Wednesday, but neither he nor Emergency Situations Minister Sergei Shoigu has explained what could have caused the flood. Both called the disaster “mysterious” last week.

While Riyadus Salikhiin has committed some of Russia’s worst terrorist attacks, Chechen rebels have also been known to claim responsibility for events they had nothing to do with. Chechen rebels said they were behind an explosion that sank the Kursk submarine in August 2000. Later that month, rebels also said they caused a fire at Moscow’s Ostankino television tower that killed three. In 2005, the rebels said they blew up an electric transformer that caused power shortages in Moscow for several hours. Rebel involvement was never confirmed in any of those cases.