Oil production from the Organization of the Petroleum Exporting Countries (OPEC) in March was 29.56 million b/d, which was 550,000 b/d lower than the 30.11 million b/d total for February, making it the lowest level of oil production from OPEC since mid-2011, according to Platts.

The decline in oil production is being attributed to insurgent attacks, which shut a key export pipeline in Iraq, and caused a renewed downward swing in Libyan production.

Saudi Arabia also reduced output because of lower refining demand due to maintenance, the report says.

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Together, Saudi Arabia, Iraq and Libya accounted for 440,000 b/d of the overall drop.

The Iraq-Turkey pipeline, which carries Kirkuk crude from Iraq's northern fields to Turkish Mediterranean port Ceyhan, remained out of action more than a month after the early March attacks on the line that forced some northern production to be curtailed, the report says.

“The Iraqi reduction is viewed as particularly unsettling,” said John Kingston, Platts global director of news. “It comes just a month after a huge jump in output that followed improvements to the country's exporting capabilities in the south. Given that the often-troubled northern pipeline continues to get hit by difficulties, I suspect the Iraqi monthly number will continue to be volatile.”