Tikrit, Iraq - Thick clouds of black smoke filled the skies as far south as Tikrit on Monday after a massive fire started near the Baiji oil refinery complex, one of Iraq's largest.

An official with the North Refineries Company, which operates the refinery at Baiji told the Kurdish AKA news agency that the fire began in an area used to burn waste from the industrial complex's five refineries.

The company official ruled out the possibility of sabotage, but said the refinery was operating at its capacity of 350,000 barrels of oil a day, or about a third of Iraq's total refinery capacity.

Baiji, some 200 kilometres north of Baghdad and 40 kilometres north of Tikrit, is the largest oil refinery in Iraq's Sunni heartland.

Four refineries in the industrial park, which was built in 1982 with cooperation from international oil companies, refine oil. A fifth produces asphalt and other petroleum derivatives. (dpa)