Bitcoin prices extended declines Thursday following a move by officials in South Korea to curb digital currency speculation that could include the closure of some domestic cryptocurrency exchanges.

Spot bitcoin prices on the Bitstamp exchange, which feeds into the CME Group futures contract, fell to as low as $13,500 by 6:15 am eastern time, taking its fall from record highs reached earlier this month to just under 30%.

CME Group futures contracts for January delivery were marked 10.5% lower on the session at $13,625 while those trading on the CBOE platform were seen $1,035 lower at $13,580 each.

The moves followed a statement South Korea's Office for Government Policy Coordination which said it would ban banks from offering virtual accounts to cryptocurrency sites and demand that digital currency transactions take place with verified names between buyers and sellers. It also said it could consider the closure of certain exchanges, if necessary, to clamp down on speculation in the surging online market.

"Cryptocurrency speculation has been irrationally overheated in Korea," the statement said. "We cannot leave the abnormal situation of speculation any longer."

South Korea is one of the world's biggest digital currency market and the Bithumb exchange, one of the most active according to Coinmarketcap.com data, is based in Seoul.

Curiously, gold appears to be a direct beneficiary to the bitcoin bear market, with prices hitting a one-month high of $1,293.25 in European trading, boosted also by a weaker U.S. dollar and falling government bond yields.

Rising metals prices -- including copper, which hit a fresh four-year high overnight -- suggest an optimistic outlook for global economic growth, especially in fast-advancing countries such as China and India, where demand remains robust.

The recent surge in metals and other commodities has boosted the value of currencies in producing nations and clipped the U.S. dollar index, which measures the greenback's strength against a basket of its global peers.

The index was marked 0.33% lower at 92.74, dragged down also by lower U.S. Treasury bond yields, which had benchmark 10-year notes pegged at 2.43%.

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