Banning the trading of artworks made of rhinoceros horns and ivory has contributed to a sharp decrease of turnover in China's booming art auction market, an industry association said Tuesday.

The total turnover of China's antique and art auctions in 2012 halved year-on-year to 27.9 billion yuan (4.5 billion U.S. dollars), the first fall since the global financial crisis in 2008.

Statistics released by the China Association of Auctioneers on Tuesday showed that the decrease was mainly caused by the fall in the number of items sold for over 1 million yuan, which were added up to 4,500, less than half of that recorded in the previous year.

A spokesman for the association said there were some policy factors that affected the art auction market in 2012.

Customs tightened imports of artworks and authorities banned the trading of artworks made of rhinoceros horns and ivory, which alone sliced an estimated 2 billion yuan off the turnover, the spokesman said.

However, the spokesman said auctioneers were not pessimistic about the sagging turnover, as active auctions of middle and low-priced artwork showed rigid demand for art collections like scripts and paintings.