Rebel attacks on oil installations cut Nigeria’s production by 10 percent in May, contributing to a drop in monthly output from the Organization of Petroleum Exporting Countries, a Bloomberg News survey showed.

Nigerian production declined by 160,000 barrels a day to 1.45 million, according to the survey. OPEC’s total crude output fell to 32.71 million barrels a day last month, from a revised 32.83 million in April.

Nigeria’s production has fallen to the lowest in almost three decades, helping to drive an 80 percent rally in oil prices since they touched a 12-year low in January. Brent, the global benchmark, is trading near $52 a barrel, the highest since October.

Kuwaiti production rebounded in May after a three-day walkout by oil workers in April. OPEC oil ministers meeting in Vienna last week decided not to re-establish an output ceiling for the group after scrapping an official target of 30 million barrels a day at their December meeting.

Bloomberg News has expanded the sources used in its monthly production survey. They now include oil companies, governments, OPEC, analysts and tanker tracking. Some estimates for April were revised to reflect the additional information.

(Source: BLOOMBERG)