China bans banks from handling Bitcoin trade
China has banned its banks from handling transactions involving the Bitcoin virtual currency.
The ban came in a notice issued by the People's Bank of China, financial watchdogs and the nation's IT ministry.
Bitcoins were a "virtual good", had no legal status and should not be used as a currency, it said.
The decision comes after bitcoins' rapid rise in value was called a "bubble" by Alan Greenspan, former US Federal Reserve chairman.
How Bitcoin works
Bitcoin is often referred to as a new kind of currency.
But it may be best to think of its units being virtual tokens rather than physical coins or notes.
However, like all currencies its value is determined by how much people are willing to exchange it for.
To process Bitcoin transactions, a procedure called "mining" must take place, which involves a computer solving a difficult mathematical problem with a 64-digit solution.
For each problem solved, one block of bitcoins is processed. In addition the miner is rewarded with new bitcoins.
This provides an incentive for people to provide computer processing power to solve the problems.
To compensate for the growing power of computer chips, the difficulty of the puzzles is adjusted to ensure a steady stream of about 3,600 new bitcoins a day.
There are currently about 11 million bitcoins in existence.
To receive a bitcoin a user must have a Bitcoin address - a string of 27-34 letters and numbers - which acts as a kind of virtual postbox to and from which the bitcoins are sent.
Since there is no registry of these addresses, people can use them to protect their anonymity when making a transaction.
These addresses are in turn stored in Bitcoin wallets which are used to manage savings.
They operate like privately run bank accounts - with the proviso that if the data is lost, so are the bitcoins owned.
The ban was imposed because bitcoins were not backed by any nation or central authority, said the notice.
It added that it was planning to step up its efforts to curb the use of bitcoins to launder cash.
Individuals were still free to trade in bitcoins but should be aware of the risks involved, said the People's Bank of China (PBOC), adding that it planned to formalise the regulation of exchanges that dealt in the digital cash.
Experts told Reuters the PBOC was moved to make its decision because Chinese nationals were heavily involved in trading the virtual currency. Many believe this is because it helps them avoid controls on trade in the yuan.Value soar
The value of bitcoins traded on Chinese exchanges fell after the announcement was made.
Interest in the virtual currency has seen its value soar in recent weeks.
On 28 November, the value of one bitcoin surpassed $1,000 for the first time.
The swift rise in value led Mr Greenspan to say the exchange rate for the virtual currency was "unsustainably high" in an interview with Bloomberg.
"It's a bubble", he said, going on to question the financial value people had pinned on bitcoins.
"You have to really stretch your imagination to infer what the intrinsic value of Bitcoin is," he said. "I haven't been able to do it. Maybe somebody else can."