Oil prices rose in early Asian trading on Monday after a three-day break, but volumes were tiny as a number of markets remain on holiday for Easter.
U.S. crude's front-month contract CLc1 was up 37 cents at 39.83 a barrel at 0055 GMT.
On Thursday, it settled down 33 cents at $39.46 a barrel, recovering from a session low of $38.33. For the week, it rose 2 cents, finishing up for a sixth straight week.
Brent's front-month LCOc1 rose 24 cents to $40.68 a barrel.
It fell 3 cents to $40.44 a barrel, after an earlier drop to $39.22, on Thursday. For the week, it fell 76 cents, or nearly 2 percent, its first decline in five weeks.
Oil prices have risen about 50 percent from multiyear lows hit in January on glut worries.
Declining U.S. oil output and strong gasoline demand were responsible for some of that recovery, but the bulk of it was powered by major producers' plans to freeze output at January's highs.
Producers are due to meet on April 17 to discuss the plan.
OPEC member Iraq's oil exports have held steady so far in March, according to loading data and industry sources, halting for now the rapid supply growth from the country.
Baghdad has given verbal support to the initiative by OPEC and outside producers to freeze output to try to boost prices.