New York: The Organisation of Petroleum Exporting Countries' oil output climbed to a four-month high in December, led by increases in Nigeria and Iraq, as rising oil prices encouraged production, a Bloomberg News survey showed.

Production gained 135,000 barrels, or 0.5 per cent, to an average 29.185 million barrels a day, according to the survey of oil companies, producers and analysts. Production by members with quotas, all except Iraq, rose by 100,000 barrels to 26.8 million, about two million above their target.

Compliance with the quotas, which took effect in January 2009 to strengthen oil prices that had tumbled to below $40 a barrel, was 53 per cent in December, down from 56 per cent in November. Prices were up 6.8 per cent on the New York Mercantile Exchange last month and touched a 26-month high of $91.88 a barrel on December 27.

Nigeria's output surged by 100,000 barrels a day to 2.22 million, a four-year high, according to the survey. It was the largest increase by any member.

Africa's biggest producer exceeded its quota by 547,000 barrels, the largest of any member as producers recovered from disruptions in November.

Those included a force majeure on production of Bonny Light crude due to a leak in the Trans-Niger pipeline and militant attacks earlier in the month that lowered output on both the Oso and Okoro fields.

Iraq, Opec's third-largest producer after Saudi Arabia and Iran, pumped an average 2.39 million barrels a day, up 35,000 barrels a day from November, according to the survey.

Iraqi oil production exceeded 2.6 million barrels a day for the first time in 20 years, newly appointed Iraqi Oil Minister Abdul Kareem Al Luaibi said last week at a press conference in Baghdad.