Oil prices slid Monday, extending last week's sharp decline as the dollar strengthens on eurozone strains and record supplies in the United States add further downward pressure.
US benchmark West Texas Intermediate (WTI) for delivery in April shed $1.17 to $49.64 a barrel compared with Friday's close.
Brent North Sea crude for April lost $1.24 to stand at $58.98 in London afternoon deals.
WTI slumped 4.66 percent and Brent tumbled 2.1 percent during the week to last Friday.
"Crude oil prices extended declines (Monday)... as investors remained cautious following the ongoing uncertainty in the eurozone, while the strong US dollar currently weighed on market sentiment," said Myrto Sokou, senior research analyst at Sucden brokers.
"Crude oil inventories continue to remain fairly high, following sharp builds of crude oil stocks in the last few weeks. The continuous large increases of crude inventories verify a possible slowdown of US oil demand," she added.
Globally, crude supplies are being boosted after oil fields in eastern Libya resumed pumping to the Hariga port after a pipeline was repaired, Bloomberg News reported.
And Oman, the biggest Middle East producer outside the Organization of Petroleum Exporting Countries, plans to ramp up output to 980,000 barrels a day this year.