Iraq began pumping oil at around 4:30 p.m., said the oil official, speaking on condition of anonymity, at Turkey's Ceyhan terminal.
"They started pumping and everything looks normal," the official said. "We don't know for how long they will keep pumping, it is up to Iraqis."
The oil flow to Turkey was expected to be between 300,000 and 400,000 barrels a day, about half of pre-war volumes, Dow Jones reported on Monday. The pipeline has a maximum capacity of over 1 million barrels per day.
Iraq resumed oil sales in June, when tankers began shipping out crude that had been in storage at Ceyhan since the war halted exports. But deliveries of fresh supplies were held up, in part because of sabotage on the pipeline (search), blamed on insurgents leading a guerrilla campaign agains the U.S.-led occupation.
Oil was expected to flow for about 10 days to Ceyhan before any ships would be sent for loading.
"First, we have to wait for the storage tanks to be filled before exports can begin," the official said.
Ceyhan already has about 500,000 barrels of Iraqi crude in stock and has a total storage capacity of around 8 million barrels.
Iraq's oil exports resumed after the U.N. Security Council in May lifted sanctions on Iraq and recognized the U.S.-led coalition's authority over Iraq and its oil revenue.