Gustav, NE (Nationalencyklopedin/the Swedish National Encyclopedia) says:
Meaning (for our English readers ):
"Siberia, Russian Sibir, area East of the Ural Mountains in Russia; 12,8 million square km, including Russian Far East. ..."
In General NE is (far) more trustworthy than Wiki.
That's the traditional English usage too, essentially Asian Russia. The Wikipedia article actually says "[t]raditionally, Siberia extends eastwards from the Ural Mountains to the Pacific Ocean".