OPEC output in May has hit its highest since 2008 as Saudi Arabia maintained high production rates despite a drop in prices and Iranian shipments did not fall substantially further ahead of an EU embargo, a Reuters survey found on Tuesday.

Supply from the 12-member Organization of the Petroleum Exporting Countries has averaged 31.80 million barrels per day (bpd), up from 31.75 million bpd in April, the survey of sources at oil companies, OPEC officials and analysts found.

OPEC's total is the highest since September 2008, shortly before it agreed to a series of supply curbs to combat recession and collapsing demand, based on Reuters surveys.