New York's main contract, light sweet crude for delivery in August, shed 80 cents to $71.34 a barrel, continuing its slide from yesterday when it had dipped below June lows.
Brent North Sea crude for August delivery fell 52 cents to $70.95.
Weak US jobs data was dragging down oil prices as well as Asian equities markets, said Victor Shum, a Singapore- based senior principal of Purvin and Gertz energy consultancy.
"The sentiment in the market has been quite bearish... The market is still reacting to the weak US private sector employment data," he said.
"This bearish sentiment is therefore putting downward pressure on oil."
Oil prices tumbled by more than eight per cent last week as weak US economic data sparked fears about the strength of the global recovery.
The US economy shed 125,000 jobs in June, official data showed Friday. Most analysts had expected a loss of 100,000 jobs.
Asian equities' weak opening today, particularly the Japanese Nikkei index, which fell 106.09 points or 1.14 per cent to 9,160.69 in the first minutes of trading, also weighed on oil prices, Shum added.
"Oil has been really handcuffed to equities.... Nikkei is down this morning, so oil is down as well."
However, Shum said prices would hold at current levels as some traders felt the market had been oversold and bought up cheap crude.