Central bankers and regulators around the world are ratcheting up warnings about bitcoin, as prices of the virtual currency soar, more merchants accept it for payment and investors pour money into new bitcoin-related ventures. Officials in China and France and from the European Union voiced their strongest concerns yet about the potential for speculative trading and money laundering in bitcoin and the potential risks for ordinary people using the currency. At the same time, a currency analyst issued a positive outlook for bitcoin investors, while a university in Cyprus announced it had accepted its first tuition payment in bitcoin. The contradictory sentiments underscore the confusion surrounding the four-year-old virtual currency. Reuters China and France on Thursday issued warnings about the use of bitcoin, saying the virtual currency didn't offer the assurances of payment that a legal currency does.