The price of bitcoin has tumbled as one of the world's largest exchanges suspends trading after losing $65 million worth of the cryptocurrency in a massive security breach.

The value of bitcoin against the dollar plunged in the aftermath of the hacking attack at Hong Kong-based Bitfinex, leaving the cryptocurrency treading water at $540, way down from a $650 weekend high.

Bitfinex has replaced its home page with a security warning, informing users of its decision to halt trading while it investigates the breach. In total, the mysterious hackers made off with 119,756 bitcoin, leaving Bitfinex customers seriously out of pocket.

"We will look at various options to address customer losses later in the investigation," says the company in a statement. "While we are halting all operations at this time, we can confirm that the breach was limited to bitcoin wallets; the other digital tokens traded on Bitfinex are unaffected. We are deeply concerned about this issue and we are committing every resource to try to resolve it."