Internet monitoring carried out from April 2007 to March 2008 revealed 30 adverts offering polar bear skins for sale. The average number of adverts per month, 2.7, exceeded figures of 2003 (1.25), 2004 (1.13) and 2007 (1.6).
The average price has doubled since 2003 to $6,000 per hide.
So far, conservation experts have established only two poaching sites - the Taimyr Peninsula on Siberia's Arctic coast and Chukotka in Russia's Far East.
"We put the number of polar bears killed at 150-200 animals per year," said Viktor Nikiforov, WWF Russia's polar bear expert.
According to the U.S. Geological Survey, two thirds of the 25,000 polar bears around the world will die by 2050, when the ice they use to hunt seals will melt due to global warming.
The Soviet Union banned hunting of polar bears in 1957. The species currently has 'vulnerable' status on the IUCN Red List.