The flow of oil through the pipeline from Iraq's Kirkuk oilfields to the Turkish port of Ceyhan was halted on Saturday morning, and repairs could last up to 72 hours, sources at Iraq's North Oil Company said.

'We do not so far know the cause, whether it was a technical glitch or sabotage,' one source said, asking not to be identified.

The key energy corridor, which carries an average of 500,000 barrels per day, or around a quarter of Iraq's oil exports, has been repeatedly targeted by suspected insurgents in recent months or has suffered technical faults that halted pumping.

The sources said repair crews had started work at dawn and that it would probably take 48-72 hours to fix the pipeline.

A bomb attack earlier this month blamed by Turkey on the outlawed Kurdistan Workers Party (PKK) halted the flow for two days. Two people were killed in the explosion, which started a fire.

It was at least the second attack since July on the Turkish side of the border blamed on the PKK since the group called off a ceasefire.

Bombings by insurgents on the Iraqi side of the border have been far more common. Saturday's rupture occurred in volatile Nineveh province, where Sunni Islamist al Qaeda retains a foothold despite a sharp fall in violence in much of the rest of Iraq.

The pipeline connects Iraq's northern oilfields around Kirkuk to Turkey's Mediterranean port of Ceyhan, where the crude is loaded onto tankers for export.

Sabotage and technical problems kept the route mostly idle until 2007 following the 2003 US-led invasion of Iraq.

The Kirkuk-Ceyhan link consists of two parallel pipelines. Different pumping stations along the route allow pipeline operators to switch the flow of crude to the alternative line, Iraqi oil-industry sources have said.-Reuters