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South Korea is considering a law to ban cryptocurrencies such as Bitcoin being traded on local exchanges.

Justice Minister Park Sang-ki said virtual currencies were "great concerns" and that the ministry was preparing a bill to ban trading.

However, South Korea's presidential office said later that a ban had not yet been finalised and was one measure being considered.

The local Bitcoin price fell by a fifth after the justice minister's comments.

In South Korea it trades at about a 30% premium compared with other countries.

There is no one fixed price for Bitcoin as it is not regulated and is traded on dozens of exchanges worldwide.

According to Coindesk.com, the price of Bitcoin was about 8% lower at just under $13,800 on Thursday afternoon.

South Korea has become a hotbed for cryptocurrency trading, accounting for about 20% of global Bitcoin transactions.

It has more than a dozen cryptocurrency exchanges, according to the Korea Blockchain Industry Association.

Several were raided this week in a probe into alleged tax evasion, including the country's second-largest virtual currency operator, Bithumb.

The government had already said in December that it would apply more scrutiny to the exchanges, including moves to curb anonymous trading.

Given the low levels of trading and relatively small number of people holding virtual currencies, wild price swings have become the norm, leading to an argument that paying too much attention to price rises and falls is futile.

Digital currencies such as Bitcoin have surged in value over the past year - driving a huge demand. That has led to concerns about gambling addiction as inexperienced investors try to ride the wave.