Bitcoin fell to a more than one-year low on Wednesday, falling below a key support level of $6,000, with traders and analysts unclear on what caused the sudden drop in price.

"The market had been entering a wedge, with the volatility so low," said Charlie Hayter, founder of industry website Cryptocompare in London, referring a technical chart pattern.

"What you are seeing low is a breakout on the downside. Sometimes when things happen, it takes a while for the true reason to become clear - an exchange trade or regulatory action."

Bitcoin fell to as low as $5,534. The $6,000 level was a key support level for bitcoin for some time. It was last down 11 percent at $5,571.61.