West Texas Intermediate (WTI), the US benchmark, fell to levels last seen in September 2003, striking USD 27.55 a barrel at one point.
At around 0500 GMT, the contract was trading at USD 27.68, down 78 cents, or 2.74 per cent. WTI had closed at USD 27.13 on September 23, 2003, after hitting an intra-day bottom of USD 27.10.
Brent crude -- which briefly fell below USD 28 on Monday to levels not seen since November 2003 -- was 48 cents lower at USD 28.28.
He also said the WTI February contract was due to expire later in the week, which could have prompted traders to roll over their positions to the March contract.
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The IEA said Tuesday oil prices are set to fall further this year as supply vastly exceeds demand, with major oil exporter Iran's return to the market offsetting any production cuts from other countries.
"Can it go any lower?" the IEA said. "Unless something changes, the oil market could drown in oversupply. So the answer to our question is an emphatic yes. It could go lower."
Prices have crashed about 75 per cent since mid-2014, hit by a perfect storm of a supply glut, weak demand, a slowing global economy and a strong dollar.
The oil crisis has caused ructions across global markets, wiping trillions of dollars off valuations, with weak demand for the commodity signalling weakness in economies. The tumbling prices have also led to major energy firms scaling back or cancelling investment and projects, and laying off thousands of workers.
"On top of that, there are further concerns that there's a stockpile to be cleared in Iran now that sanctions have been lifted," he told AFP by telephone from Sydney.
"Coming on top of a very fragile pricing environment, that's clearly had an impact."
Iran on Monday ordered a boost to crude production a day after the West lifted sanctions on the country in response to Tehran's compliance with a deal on curbing its nuclear programme.
"It's the supply side that is getting the focus at the moment. The demand aspect is a longer term proposition for the market," added McCarthy.
"We're now outside fundamentals and for that reason it is very difficult to forecast where it will stop. When markets panic, they become unpredictable.