Bitcoin plunged Friday, taking the digital currency briefly below $11,000 and down 44 percent from a record high hit at the start of the week.

Bitcoin had rallied to a record high above $19,800 on Sunday and was trading near $15,500 for much of Thursday New York time, according to Coinbase. But an afternoon selloff accelerated into the night, and bitcoin dropped 30.2 percent Friday morning to a low of $10,400 on Coinbase. It was trading back near $12,750 mid-morning Friday.

There were no immediately apparent explanation for the selloff and extreme volatility.

At its lows, bitcoin had fallen 47 percent in just five days and lost about $9,400. The digital currency erased more than $1,000 in one hour alone Friday morning.

Bitcoin one-hour performance

Source: Coinbase

Bitcoin futures also tumbled Friday. The CME bitcoin futures expiring in January, which launched Sunday, reached “limit down,” falling nearly 20 percent to $12,265 in morning trading before recovering slightly to $12,760. Markets were still open for trading.

The Cboe bitcoin futures contract, which launched on Dec. 10, briefly dropped 21 percent to $12,050 after triggering a brief, built-in trading halt due to price volatility. The futures were last trading 17 percent lower.

The bitcoin offshoot, bitcoin cash, collapsed, temporarily falling 40 percent Friday to $1,873, after topping $4,000 two days ago, according to Coinbase. Bitcoin cash recovered to trade near $2,200 in mid-morning trading.

Coinbase is the leading U.S. platform for buying and selling major digital currencies, and also operates an exchange for institutional investors called GDAX. On Tuesday, Coinbase surprised many by announcing it was launching trading in the bitcoin offshoot, bitcoin cash. The company had said for months it would allow withdrawals of bitcoin cash on Jan. 1, 2018, and notify customers of other changes beforehand.

In the last several days, many Reddit and Twitter users have also complained they are unable to complete transactions smoothly on Coinbase. The company said on its status website that since last Friday, high transaction volumes were delaying wire transfers. A Wednesday update said “wire deposits and withdrawals may be delayed by up to 5 business days.”

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The sharp drop in the cryptocurrency prices came as demand from South Korean and Japanese investors fell. The two countries had dominated trading volume for major cryptocurrencies in the last several months.

On Tuesday, the owner of the South Korean Youbit digital currency exchange filed for bankruptcy after a hack resulted in the loss of 17 percent of its assets. The Wall Street Journal reported Wednesday, citing sources, that South Korean officials are investigating the possible involvement of North Korea in the hack.

Bank of Japan Governor Haruhiko Kuroda called the surge in bitcoin prices “abnormal” at a media conference on Thursday.

“These don’t concern me for the long-term because we’ve seen more and greater issues in the past,” said Joe DiPasquale, founder and CEO of BitBull Capital, a cryptofund that invests in other cryptofunds. He said BitBull has about $20 million in assets under management.

“Right now people are biding their time until the bottom is felt,” DiPasquale said, citing his conversations with cryptofund managers. “It is a buying opportunity, perhaps in the next day, but you have to see where support is reached to make that decision.”

Stocks such as Riot Blockchain that have soared dramatically on speculation around their connection to bitcoin and its underlying blockchain technology also traded lower Friday morning by double-digits.

— CNBC’s Todd Haselton and Yen Nee Lee contributed to this report.