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By Randy Fabi

BAGHDAD, March 28 (Reuters) - Iraq's southern oil pipeline system was flowing at near normal levels to its Basra export terminal after the two main pipelines were left undamaged during an attack on Thursday, an Iraqi oil official said on Friday.

"As of 10 p.m. (1900 GMT) last night, things are back to normal," the senior official told Reuters on condition of anonymity.

Saboteurs attacked the southern oil pipeline system on Thursday, briefly suspending exports from the south of the country for the first time in years.

The resulting blaze prompted the Southern Oil Company to shut down the pipeline system, which pumps about 1.5 million barrels per day to the Basra terminal, as a precaution, he said.

After the fire was extinguished on Thursday an investigation showed that a smaller, 28 inch pipeline, pumping about 100,000 barrels per day, was damaged.

The two main pipelines, which are located nearby and are more than 40 inches in diameter, were not affected by the attack.

"When the fire erupted, they didn't know which one was damaged and they had to shut all of them," the official said. "When they put the fire out, they discovered it was the smaller of the three."

Backup pipelines from southern oilfields have kept flow levels to the terminal near normal, he said.

The pipelines are located about 7 km south of oil-rich Basra, where heavy clashes between Iraqi security forces and Mehdi Army militants have occurred this week.

Iraq's government relies heavily on oil exports for revenue, and had managed to sustain the flow from Basra even as a violent insurgency targeted the country's oil installations elsewhere.

In the north, persistent sabotage and technical problems had reduced exports to a trickle since the U.S.-led invasion in 2003, but flows have improved greatly since last summer. (Reporting by Randy Fabi; Editing by Michael Urquhart)

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