BITCOIN and other cryptocurrencies including ethereum, litecoin and ripple plummeted in value on Monday after Coinmarketcap removed prices from South Korean exchanges without warning.

Prices on South Korean exchanges are typically up to 30 per cent higher than in other countries. The widely used research site’s decision to exclude average price data from Bithumb, Coinone and Korbit resulted in a sudden drop in displayed prices.

That caused confusion among investors and partly contributed to a major sell-off, which was also fuelled by news that South Korean and Chinese regulators planned to increase oversight on cryptocurrency trading and mining.

“This morning we excluded some Korean exchanges in price calculations due to the extreme divergence in prices from the rest of the world and limited arbitrage opportunity,” Coinmarketcap wrote on Twitter. “We are working on better tools to provide users with the averages that are most relevant to them.”

The total market capitalisation of more than 1300 cryptocurrencies tracked by Coinmarketcap fell from around $US830 billion ($A1056 billion) to bottom out at $US669 billion ($A851 billion) on Monday, a drop of 20 per cent. By late Monday, the market was sitting at around $US742 billion ($A944 billion).

This morning we excluded some Korean exchanges in price calculations due to the extreme divergence in prices from the rest of the world and limited arbitrage opportunity. We are working on better tools to provide users with the averages that are most relevant to them. — CoinMarketCap (@CoinMarketCap) January 8, 2018

Right, might be useful to notify people of things like this before or as you execute to avoid crashing the market, thanks. — Zineb Belmkaddem (@Onlyzineb) January 8, 2018

Really unprofessional. You ought to have announced this many days in advance & given fair warning to people who depend on your website for accurate movements in markets. New unannounced calculation, fake news websites like @coindesk published hit-peices on $xrp - repeated by MSM — Dr. Trumpsta (@XRPTrump) January 8, 2018

Very unprofessional!!! How about an apology to many people who started to panic sell $xrp based on what you showed to be a false positive crash! And an apology to many people who lost anywhere from $100-thousands of dollars due to the panic sell?! — joe (@JoeySparkz17) January 8, 2018

Coinmarketcap Is supposed to show GLOBAL prices for cryptocurrencies - if you start excluding regions and exchanges, then that makes your service unreliable and untrustworthy. — Lev Knoblock (@ItsLevalicious) January 8, 2018

Among the hardest hit were ripple, litecoin and bitcoin cash, which at the time of writing were down 25 per cent, 11 per cent and 13 per cent respectively on the previous day, while bitcoin was trading at $US15,215 ($A19,364), down more than 7 per cent.

“The most obvious point is how undeveloped the ecosystem supporting bitcoin and cryptocurrency trading still is,” said ABC Bullion chief economist Jordan Eliseo.

“It highlights the undeveloped nature of trading in bitcoin, reporting in bitcoin, market data sources for people to utilise when they’re wanting to track performance or monitor trends in that space.

“You can look at it two ways and say Coinmarketcap taking Korean prices out of their averages makes the performance of bitcoin and cryptos look worse than they otherwise would, [but] the flip side is that in the past they weren’t reporting them accurately.”

The move drew fierce criticism from the cryptocurrency community. “Right, might be useful to notify people of things like this before or as you execute to avoid crashing the market, thanks,” one commenter wrote on Twitter.

“Really unprofessional,” another said. “You ought to have announced this many days in advance and given fair warning to people who depend on your website for accurate movements in markets.”

Others weighed in on the broader implications. “How healthy is a market really if a single non-exchange website can crash it?” one commenter on Reddit asked.

It came after a series of reports last week that suggested Chinese officials planned to crack down on bitcoin miners, the networked computers which work to verify transactions on the blockchain and in return receive newly created units of the currency.

Bitcoin mining consumes an enormous amount of energy — 38.6 terawatt-hours a year, or 0.17 per cent of total world consumption, according to Digiconomist. That’s more than the individual energy use of a number of countries including Denmark.

The reports in Reuters, Bloomberg and Caixin Global suggested authorities planned to abolish preferential electricity deals and tax deductions for bitcoin mining companies in order to “guide” them towards an “orderly exit” from the country.

Meanwhile, South Korean authorities have reportedly begun inspections at six banks that provide accounts to companies involved in cryptocurrency trading, citing concerns about potential money laundering.

Last month, Australian exchange Coinspot suspended deposits in Australian dollars due to ongoing problems with local banks, which were accused of closing accounts and blocking transactions.

“The regulatory noise in South Korea and China, that’s going to be an ongoing threat to bitcoin and to crypto more generally for the foreseeable future,” said Mr Eliseo. “Governments, financial institutions, you name it, are still working out how best to deal with crypto and the businesses involved with it.”

Mr Eliseo said it was a “real risk factor” investors needed to be aware of. “While it’s very easy to get money into this system to buy cryptocurrency, it may not be so easy to get it out when you want to liquidate your position, realise profit and get your money back into the banking system,” he said.

“There is enormous opacity surrounding the vast majority of the leading cryptocurrency exchanges. I think a lot of people, when they buy bitcoin on an exchange, they think they’re actually buying a specific bitcoin or portion of a bitcoin, whereas I suspect what they’re really buying is a claim on that bitcoin.

“In that sense it’s broadly analogous to a bank, which doesn’t have a whole heap of banknotes waiting for you to come pick them up, but the big difference is there is absolutely zero governance over these big exchanges. With a bank, the government is there to protect depositors.”

It came amid reports that Microsoft was no longer accepting payment in bitcoin, following a similar move by online game distribution platform Steam last year “due to high fees and volatility”.

The news was reported by industry blog Bleeping Computer, which cited “several Microsoft employees who have told us the move is temporary and cited the unstable state of the bitcoin currency”. Microsoft did not immediately respond to requests for comment.

frank.chung@news.com.au