Values for benchmark Oman crude fell on Monday on poor demand from Asian refineries that were undergoing regular maintenance.
Physical cargoes of April Oman were pegged at around $2.40 to $2.50 above Dubai quotes, down from premiums near $3.00 seen last week.
Oman premiums had gained last week on stronger-than-expected buying from Thai and Indian refiners.
A cargo of April Qatari al-Shaheen crude was believed to have been sold at around $2.20-$2.50 a barrel to Dubai quotes, roughly in line with deals done earlier this month, traders said.
Petral, the trading arm of Indonesian national refiner Pertamina, bought its first Qatari condensate cargo in a tender for May delivery as it seeks to widen its crude selection, trade sources said on Monday.
In the latest tender, Petral bought 500,000-600,000 barrels of deodorised field condensate (DFC) and 730,000 barrels of Russian ESPO Blend crude, the sources said.
Both cargoes were sold by traders and prices were linked to dated Brent on a cost-and-freight (C&F) basis, although the premiums were not immediately known.