Does anybody know what this is?

Serbian.

Can anybody tell us if this is another nuclear explosion (in the vein of Chernobyl), in Sverdlovsk in Russia? (There is [was?] a nuclear power plant there, so…) Or is it something else? The authorities never tell us the truth about anything, so I would like to know if anybody out there knows something about this.

Related post: About the coming Deluge.