The two natives of Russia's volatile North Caucasus region had since September been preparing a "terrorist act" at the chemical storage facility in the central Kirov region that could have put the lives of "hundreds of people" at risk, investigators said in a statement.
"According to the investigators, the suspects are Wahhabi followers and have come to the Kirov region from Moscow," the statement said, referring to an ultra-conservative branch of Islam.
"The act was being prepared with the aim of influencing decision-making by authorities and international organisations," the statement said without providing specifics.
The leader of Russia's Islamist rebels, Doku Umarov, has been seeking to impose an Islamist state throughout Russia's mainly Muslim Northern Caucasus region and has for years been waging deadly insurgency against the Russian security forces there.
He has also ordered his foot soldiers to target Russian infrastructure outside the troubled North Caucasus. The group claimed several atrocities including a deadly Moscow airport bombing in 2011 and a metro attack in 2010.