MtGox bitcoin chief Mark Karpeles charged in Japan

The founder of MtGox - once the world's biggest Bitcoin exchange - has been formally charged by prosecutors in Japan with embezzlement amid an investigation into losses of nearly $400m.

Japanese police arrested Mr Karpeles in Tokyo, where he lives, on 1 August.

His arrest was connected to the MtGox loss of 850,000 Bitcoins in February 2014.

At the time, the losses were worth nearly $400m (about £240m).

It was claimed the Bitcoin losses were caused by a bug - but the Tokyo-based exchange later filed for bankruptcy.

MtGox then said it had found some 200,000 of the lost bitcoins.

Mr Karpeles has also been accused of falsifying data and improperly transferring MtGox funds.

The French-born former chief executive of the exchange had been held in detention for six weeks without being formally charged, which is allowed under Japanese law.

It was not clear if the embezzlement charge was related to all or some of the missing money.

Japan's Kyodo News said in August that a lawyer acting on Mr Karpeles' behalf denied his client had done anything illegal.

Bitcoin is money that is completely virtual and is regarded as an online version of cash. It can be used to buy products and services.

Bitcoin developer Mike Hearn told the BBC last month there was still much confusion over the legal status of Bitcoins in many nations.