The global benchmark brent crude slipped 6.3 per cent to $56.54 per barrel today, below the 100-day average, amid the Greek debt crisis and continued turmoil in China's battered stock markets.
The selloff deepened from earlier today, when prices collapsed below the $60 per barrel mark for the first time since mid-April, hitting $58.89 per barrel.
Read more: Brent crude's back below $60
Commodities were hit after last night's referendum in Greece ended with a "no" vote against accepting bailout conditions from the country's so-called "troika" of lenders in return for unblocking aid.
While Greece's lenders have insisted they will not enter into further renegotiations, Prime Minister Alexis Tsipras has said that a "no" vote will put the Greeks in a stronger position.
They were suffered as Chinese brokerages and fund managers promised to buy more stocks as Beijing unleashed an series of measures to prop up its struggling stock market.
And additional downward pressure came from Iran and global powers which are working towards a self-imposed July 7 deadline, bringing more supply to the market if sanctions on Tehran are eased.