Bitcoin extended losses for a third day, tumbling 12 percent Sunday as South Korean cryptocurrency exchange Coinrail said there was a "cyber intrusion" in its system.

The largest cryptocurrency declined to $6,749 as of 2 p.m. in New York, the biggest drop since March 14, according to data compiled by Bloomberg from Bitstamp pricing. That widens Bitcoin’s losses for the year to 53 percent. Peer cryptocurrencies Ethereum and Ripple fell 11 percent and 12 percent, respectively.

Coinrail said in a statement on its website that it’s reviewing its system due to hacking attempts. The exchange says it has managed to freeze all exposed NPXS, NPER and ATX coins, and that other cryptocurrencies are now being kept in a cold wallet. The statement is the only content available on the exchange’s homepage, and contact information could not immediately be located.

The exchange trades more than 50 different cryptocurrencies and was the 98th largest, with a 24-hour volume of about $2.65 million, according to data from Coinmarketcap.com.