The International Energy Agency, which has headquarters in Paris, said Tuesday oil production from the 12 members of OPEC declined 535,000 barrels per day in December year-on-year. OPEC's December production, however, was 310,000 bpd higher than the previous month.
OPEC said in its January market report demand for its crude oil declined because of production increases from North America. The IEA said 11 of the 12 members of the OPEC cartel, including Libya, were reporting production gains, reversing four months of decline.
"Iraq was the only member to post a decline, though beleaguered Libya saw only a modest rise, amid government expectations of an imminent recovery in oil output," the IEA said in its market report.
Violence has increased in Iraq this month as Iraqi Prime Minister Nouri al-Maliki struggles to contain al-Qaida activity. The central government, meanwhile, is at odds over oil export plans from the semiautonomous Kurdistan Regional Government.
The central government says KRG oil ambitions may violate national laws.
OPEC said Iraqi oil production declined 1.8 percent from November to settle at 2.9 million barrels per day in December.