Other major cryptocurrencies also weakened markedly.
Bitcoin traded as low as $6,455.91 early on Wednesday Asia time, its lowest level since April. Bitcoin pared some of those losses to trade around $6,550.76 by 11:40 a.m. HK/SIN, according to CoinDesk.
Bitcoin had fallen around 10 percent over the weekend following news that South Korean exchange Coinrail had been hacked, with a number of lesser-known cryptocurrencies such as Pundi X counting among those affected. Bitcoin, however, was not mentioned by the exchange in its statements, according to Google translate.
The continued downward move was unlikely a result of last week's hack, which saw a limited level of damage caused, said Mati Greenspan, senior market analyst at eToro.
"The narrative that such a small hack caused such a large price reaction has definitely been overplayed," he said, adding that bitcoin's drop on Sunday was caused by a technical correction.
Over the last 24 hours, bitcoin has seen a dip of more than 4 percent, according to CoinMarketCap. So far in 2018, the cryptocurrency is down more than 50 percent.
Chart analysts have indicated that bitcoin's move below the $7,000 mark suggested a speedy recovery was unlikely.
As for other crypto assets, the last day has proven challenging.
Ethereum, the second-largest cryptocurrency by market capitalization, was down almost 6 percent in the last 24 hours, CoinMarketCap data showed. Ethereum stood at $499.54 at 11:40 a.m. HK/SIN, according to CoinDesk.
Ripple was also lower by nearly 6 percent in the last 24 hours, according to CoinMarketCap. It traded at 56 cents at 12:15 p.m. HK/SIN.
— CNBC's Evelyn Cheng contributed to this report.