Brent oil prices slumped to a 17-month low on Wednesday, as traders fretted over a global supply glut ahead of the latest US crude inventories report.
In early morning deals, Brent North Sea crude for October sank to $98.80 per barrel -- the lowest point since May 1, 2013. It later stood at $99.08, down eight cents from Tuesday's closing level.
US benchmark West Texas Intermediate (WTI) for October delivery dipped four cents to $92.71 a barrel.
The Brent contract had plunged on Monday under the psychological barrier of $100 for the first time in more than 14 months, weighed down by abundant supplies.
Later on Wednesday, the US government's Department of Energy (DoE) will publish its report on commercial oil inventories for the week ending September 5. 
"Brent futures extended losses ... breaching $99 per barrel ahead of the release of the weekly DOE oil inventories report," said senior research analyst Myrto Sokou at the Sucden brokerage in London.
"The release of the US weekly DOE oil inventories figures could provide an outlook about the current stock levels."
The report is a key focus for the oil market because the United States is the top global crude consumer, followed by number two China. 
"The US stockpiles numbers out later today are in focus at the moment," David Lennox, resource analyst at Fat Prophets in Sydney, told AFP.
"It will give an indication of US demand as markets waver about the health of the global economy following a batch of weak economic data.
Reserves are expected to have fallen by 1.2 million barrels in the week to September 5, according to analysts polled by the Wall Street Journal. 
Gasoline stockpiles are expected to be unchanged, while stocks of distillates, including heating oil and diesel, are expected to have risen by 600,000 barrels. 
Lennox added that investors are closely monitoring the slide in Brent, which is largely affected by international markets, following concerns about a global supply glut. 
"European demand remains exceedingly weak, but we see the North Sea producers still trying to keep up production levels to gain market share and knock out OPEC producers," Lennox said, referring to the OPEC oil cartel which is dominated by Middle East nations and accounts for one third of global production. 
Analysts have said OPEC could respond to declining prices and the global supply glut by reducing oil production levels. 
OPEC will hold its next scheduled output meeting on November 27 in the Austrian capital of Vienna, where the 12-nation cartel is headquartered.