Dado Ruvic | Illustration | Reuters

Bitcoin tumbled 10 percent on Sunday to its lowest in two months, after a relatively small South Korean exchange said it was hacked.

Over the weekend, crypto exchange Coinrail tweeted that it was hacked, and noted that lesser-known cryptocurrencies such as Pundi X were among those affected, according to Google Translate. The Pundi X-bitcoin pair is the most-traded on Coinrail, CoinMarketCap data showed.

However, Coinrail’s public statements did not mention bitcoin, according to Google Translate.

Nevertheless, Bitcoin hit a low of $6,647.33, its lowest since April 9, according to CoinDesk’s bitcoin price index, and coincided with a broader crypto sell-off. The largest cryptocurrency by market capitalization remains about 50 percent lower for the year so far.

Bitcoin three-month performance

Source: CoinDesk

Other major cryptocurrencies also fell. Ethereum dropped 14 percent to near $514 and litecoin fell more than 11 percent to around $104, according to CoinDesk.

The declines followed a report on Friday from The Wall Street Journal, citing sources, that U.S. regulators are investigating potential price manipulation at four major cryptocurrency exchanges: Bitstamp, Coinbase, itBit and Kraken.

The exchanges, CME and the Commodity Futures Trading Commission did not immediately respond to a CNBC request for comment on Sunday evening.