Crude prices collapsed to an eight-week low last week as renewed concerns over the pace of economic recovery triggered a sell-off in both equities and commodities.

An unexpected buildup in US crude inventories also pressured crude prices. West Texas Intermediate settled on Friday at $66.02 a barrel, down more than $6 from a week earlier.

The US dollar rebounded to $1.469 against the euro as investors switched from riskier assets to the safe-haven greenback on increasing fears over the slow recovery of the US economy. The Federal Reserve kept interest rates unchanged at 0-0.25%, but will slow its purchases of mortgage-related debt in order to avoid igniting inflation. However, the dollar fell on Friday after the G-20 meeting pledged to keep stimulus measures in place until the global economy recovers.

US crude stocks for the week ended Sept 18 surprisingly rose by 2.8 million barrels to stay at a five-year high of 335.6 million, against the forecast rise of 1.5 million, as imports rebounded and demand from refineries fell. Gasoline inventories grew by 5.4 million barrels to 213.1 million with the end of the summer driving season. Distillate stocks increased 3.0 million barrels to a 26-year high above 175 million. The large stock buildup suggested that energy demand will be slow to recover.

Another sign of weak demand was seen in Japanese crude imports, which tumbled for the seventh consecutive month in August by 12.4% from a year earlier. The 7% decline in domestic demand was due to the economic downturn, an ageing population and a switch toward greener energy. On the other hand, oil demand in China rose for the fifth month in August by 2.9% year-on-year, boosted by massive stimulus spending. But gasoline and diesel exports hit five-year highs as new refining capacity outpaced domestic demand.

Some support for crude prices came from demand recovery for Opec crude. The cartel's exports rose 160,000 barrels to 22.49 million bpd. Saudi Arabia's oil minister said he did not expect Opec to cut its quota next year as demand would grow with the recovery.

Thaioil estimates that crude prices this week will fluctuate within the range of $65 to $70 a barrel.