More information here, but in brief Federal Security Services detained two men, aged 19 and 22, both from the Caucasus, after they planned to plant an explosive device at the Kirov Chemical Munitions Storage facility. Russian authorities say that if the attack had been successful it would have caused hundreds of deaths. The men were part of the Wahhabi sect and had travelled from Moscow to Kotelnich, where they had occupied an abandoned house. Clearly men of Muslim persuasion living in abandoned property sets off trip wires (!) and security officials who searched the building found extremist literature, HME components and ‘foreign passports’ (not explained why this is a crime!). One of the suspects was accused of resisting arrest and their names have not been released.
There is a slight concern that this is a chance to smear Chechen/Caucasus separatists with potential CWA attacks in the shadow of Ghouta, but importantly this is not a plot to create the agent, which would smack of black propaganda, but instead attacking Russian agent in situ, which has the ring of authenticity about it. CWA storage facilities, at least in the US, and one would hope Russia, are one of the strongest points of the chain, in much the same way that nuclear reactors are, and any probes against them are likely to fail. The worry is that if they remain high on the target list then either they will be attacked indirectly, or toxic industrial chemicals will be preferred, both of which are much easier targets.