Oil prices fell by more than $1 to a six-week low of under $79 a barrel today.
For June delivery, US crude dropped $1.10, around 1.3%, to $78.87 a barrel by 0702 GMT, while London Brent crude fell 85¢ to $81.76 a barrel, according to Reuters.
Markets across Asia tumbled as worries grew as the euro fell to a 14-month low.
Investors remained sceptical about Greece's ability to carry out the tough measures it promised in return for a €110bn aid package from the EU and the International Monetary Fund.
Energy Information Administration data showed petrol stocks rose 1.2 million barrels to 224.9 million barrels.