The security chief for the oil fields in northern Iraq has been assassinated, in the latest attack on the industry.
Iraq's main oil export route will be out of action for several days
Police said Ghazi al-Talabani was shot by gunmen as he travelled to work in the city of Kirkuk.
The killing came a day after the main export pipelines in both northern and southern Iraq were sabotaged.
It was the third assassination of an official in less than a week, amid escalating violence in the run-up to the 30 June handover of power.
Iraq's interim Deputy Foreign Minister Bassam Qubba was killed by gunmen in Baghdad on Saturday, followed the next day by the killing of an education ministry official, Kamal al-Jarrah.
Bomb attacks on Monday and Tuesday shut down all crude oil exports from Iraq's southern terminals Basra and Khor al-Amaya - Iraq's main export route.
Experts say repairs will take up to 10 days. The suspension of exports will cost Baghdad nearly $60m a day, analysts said.
Benchmark US crude prices for July delivery rose 21 cents to $37.40 a barrel on Wednesday on news the attacks had halted exports.
There was also an attack on a pipeline in northern Iraq on Tuesday evening.
North Oil company officials said the explosion between Dibis and a pumping station near Kirkuk was aimed at harming Iraq's development.
The pipeline from the oilfields around Kirkuk to Ceyhan in Turkey has barely been in operation since the war because of repeated sabotage.
BBC business reporter Mark Gregory says 90% of Iraqi government revenues comes from oil, and the flow of funds is essential to pay for the country's reconstruction.
Recently crude exports have been running at around 1.7m barrels of oil a day, with 1.6m of that coming from the southern terminals. Exports have now been cut by as much as two-thirds.
Officials recognise there is now no chance of meeting a target of pumping 2m barrels a day in time for the transfer of sovereignty on 30 June, our correspondent says.
Iraqi oil exports are still below the pre-war level, even though a 14,000-strong Iraqi guard force has been set up specifically to protect pipelines and other vital parts of the oil infrastructure from attack, he says.
According to Iraqi Prime Minister Iyad Allawi, pipeline sabotage has cost the country more than $200m in lost revenues over the past seven months.