Local news reports said the corpse with a "mysterious skull" was found by two residents next to the River Kovashi, on Sunday, in the Russian town of Sosnovy Bor, a town built in 1958 to serve the Leningrad Nuclear Power Plant.

It is said that the locals, who spotted it by chance, initially believed it could be a mutant chicken embroyo that had been discarded.

However, local experts have been so far unable to say what it is.

One researcher was quoted as saying: "It seems that this body is neither fish nor fowl - this creature has a mysterious skull, no neck and wings."

The body was also looked at by experts from the Institute of Biophysics in Krasnoyarsk, who said it was impossible to make a quick identification.