19,000 Bitcoin - valued at around $275 each, so $5 million together - have been stolen from a majour European Bitcoin exchange, reports RT.

Bitstamp, a four year old company based in the UK and Slovenia is described by the Financial Times as "the world's third busiest Bitcoin exchange". It immediately took action, halting withdrawals and advising customers not to make any deposits until operations return to normal. At the time of writing, the exchange is still down.

Bitstamp's chief executive and co-founder Nejc Kodrič stated on Twitter that the majority of the exchange's Bitcoin are held in 'cold storage' - meaning that they are on computers not connected to the internet to prevent cyberattacks.

CNN's money channel describes the 19,000 Bitcoin as a "fraction of" the firm's total reserves, and that all balances would be repaid in full.

In a statement issued on the Bitstamp website, the company explained that the website is down until they "transfer a secure backup of the Bitstamp site onto a new safe environment."

"On January 4th, some of Bitstamp’s operational wallets were compromised, resulting in a loss of less than 19,000 BTC. Upon learning of the breach, we immediately notified all customers that they should no longer make deposits to previously issued bitcoin deposit addresses," the company explained. "As an additional security measure, we suspended our systems while we fully investigate the incident and actively engage with law enforcement officials."

The company went on to promise that the site will be online again "in the coming days", and that customers can stay abreast of the situation through their Twitter account, and via their own customer support.