Bitstamp, one of the largest exchanges for trading the digital bitcoin currency, said on Tuesday it had halted withdrawals on its platform after discovering "inconsistent results reported" by its bitcoin wallet, which it attributed to a denial-of-service attack. Slovenia-based Bitstamp is the second major bitcoin exchange to halt customer withdrawals recently, rattling participants in the nascent market. Last Friday, Tokyo-based Mt. Gox halted withdrawals and has yet to restart them, a development that sent bitcoin prices spiraling lower. In a statement on its website, Bitstamp said withdrawals that failed on Monday and Tuesday would be canceled, and "the amounts added back to the customer account balances." On Bitstamp's exchange, the bitcoin price was quoted at about $645, down about 6 percent on the day.