Thursday's drop to as low as $9,022 on the Luxembourg-based Bitstamp exchange left bitcoin trading at less than half the peak price of almost $20,000 it reached in December. It slid more than 26 percent last month, in its worst monthly performance since January 2015.

Other cryptocurrencies, including Ripple, the third-largest by market value, and Bitcoin Cash, have also racked up double-digit declines in the last 24 hours, according to Coinmarketcap.com, which tracks the industry. Ethereum was up slightly on the day.

Read: South Korea Says No Plans to Ban Cryptocurrency Exchanges

Last year's explosive rise in the value of digital coins and the flood of new retail investors drawn to the market have rattled global regulators nervous about a sector used largely for speculation.

Officials have also warned cryptocurrencies can be used by criminals to launder money. India, which has likened the market to a Ponzi scheme, on Thursday vowed to eliminate their use.

Facebook said in a post on its website this week that it was banning all advertising that "promote financial products and services that are frequently associated with misleading or deceptive promotional practices, such as binary options, initial coin offerings and cryptocurrency".

It was not clear whether the ban would affect all cryptocurrency adverts on the social media site. Facebook could not immediately be reached for comment.

REUTERS