LONDON, April 1 Reuters Oil prices added to recent gains on Monday amid expectations of tighter supply from OPEC cuts and attacks on Russian refineries while upbeat Chinese manufacturing data supported the outlook for improving demand.

Brent crude was 25 cents, or 0.3, higher at 87.25 a barrel by 0830 GMT after rising 2.4 last week. U.S. West Texas Intermediate crude was at 83.44 a barrel, up 27 cents, or 0.3, following a 3.2 gain last week.

Trading volumes were thin as markets in several countries remained closed for the Easter holidays.

Both benchmarks posted a third consecutive month of gains in March, with Brent holding above 85 a barrel since the middle of last month.

The Organization of the Petroleum Exporting Countries OPEC and its allies, a group known as OPEC, has pledged to extend production cuts to the end of June which could tighten crude supply during summer in the Northern Hemisphere.

Russian Deputy Prime Minister Alexander Novak said on Friday that the country39;s oil companies will focus on reducing output rather than exports in the second quarter in order to evenly spread production cuts with other OPEC members.

Drone attacks from Ukraine have knocked out several Russian refineries, which is expected to reduce Russia39;s fuel exports.

Geopolitical risks to crude and heavy feedstock supplies add to strong secondquarter demand fundamentals, Energy Aspects analysts said in a note.

Almost 1 million barrels per day bpd of Russian crude processing…