The Joint Organizations Data Initiative, a project supervised by Riyadh's International Energy Forum, said oil production from Saudi Arabia declined by 20,000 barrels per day in June to 9.6 million. Iraqi and Kuwaiti oil production followed a similar trend, with 6 percent declines reported from May to June.
Independent Kuwait oil analyst Kamel al-Harami told Bloomberg News the JODI assessment was mixed, however.
"Exports were low from OPEC countries, as demand was low in June, but production was high in many of them since local demand for summer is pushing consumption up," he said in an interview published Sunday.
OPEC said in its August monthly market report outages in member states Iraq and Libya were in part to blame for oil prices hovering above the $100 per barrel mark for much of the second quarter of 2013.
The report said it's more difficult to get Iraqi oil out of the country because of frequent acts of sabotage on the energy infrastructure.
For foreign markets, OPEC is adjusting to a North American market that relies less on imports to meet oil demand. U.S. oil production is such that imports are at 40 year lows.