By Seyhmus Cakan

DIYARBAKIR, Turkey (Reuters) - A fire on a pipeline carrying about a quarter of Iraq's oil exports forced the closure of the link on Monday and halted loading at Turkey's Ceyhan export terminal, security and shipping sources said on Monday.

The cause of the fire on the Kirkuk-Ceyhan pipeline in Turkey's Sirnak province near the Iraqi border was not immediately known, but authorities suspected sabotage, security sources said.

The fire was extinguished and workers tried to cool the pipeline, a 600-mile-long double link.

Turkish energy officials in Ankara confirmed oil flows were still suspended and said it was not immediately clear how long repairs would take.

An Iraqi Oil Ministry spokesman said Iraq had halted exports due to the fire, which broke out at 12:35 a.m. (2135 GMT), and that it expected Turkey to open the link's second pipe to resume exports.

"We were informed by the Turkish authorities that a blast and then a fire ignited on the 40-inch export pipeline on the Turkish side and we had to halt the crude flow," the ministry's Asim Jihad told Reuters in Baghdad.

"We demand that the Turkish authorities work without any delay to repair the damage quickly and to help switch the flow to the second 46-inch alternate line to ensure no more disruption to Iraq's exports to Ceyhan port," he said.

Between five and 10 tankers waited to load at Ceyhan, shippers told Reuters.

Storage tanks have about 500,000 barrels of oil, not enough to meet the tankers' capacity, one shipper said.

The pipeline, which last month exported 300,000 barrels of oil a day, is frequently shut due to sabotage. Most recently, a fire closed it on August 6.

The outlawed Kurdistan Workers Party (PKK), an armed group fighting the Turkish military in southeastern Turkey, has targeted the link in the past, calling it a strategic asset.

(Additional reporting by Ayla Jean Yackley in Istanbul, Orhan Coskun in Ankara and Ahmed Rasheed in Baghdad, editing by Nick Tattersall and William Hardy)