ICE October Brent Monday settled 62 cents lower to close at $100.20/barrel, after dropping below the $100 level for the first time since June 2013 on macroeconomic concerns.
ICE Brent fell as low as $99.36/b at 0955 EST (1355 GMT), a level not seen since May 2013, before rebounding.
NYMEX crude settled down 63 cents to $92.66/b. The October contract hit an intraday low of $91.80/b.
In refined products, NYMEX October RBOB was down 2.15 cents to $2.5619/gal, while October ULSD was down 0.98 cent to $2.8094.
"Last week was bearish, and today was a continuation of that," said Kyle Cooper, an analyst at IAF Advisors. "People are concerned about global growth, and even though they might be dismissing last week's jobs report as a one-off, it still wasn't good," he said.
A Labor Department jobs report released last Friday showed fewer jobs were added in August than analysts had expected.
Chinese imports, meanwhile, fell 2.4% in August on a year-to-year basis, the General Administration of Customs said Monday. Analysts had anticipated a 1.7% rise.
"For the most part, crude is rangebound, though right now it is testing the lower range, especially WTI," Carl Larry, president at Oil Outlooks.
"There is a lot of fear about maintenance season, and how much it'll weigh on oversupply in the US, though some of that concern might be overhyped," he said. "People are still scrambling for a news story, and just skating along until the EIA numbers come out Wednesday."
The US Energy Information Administration will release its weekly commercial inventory report Wednesday.
