A suicide bomber in a truck packed with explosives killed a senior police commander involved in an operation against Islamic State militants who have been surrounding Iraq's biggest oil refinery for months, security sources said.
Friday's attack killed General Faisal Malik, one of the supervisors of a campaign designed to break the Sunni insurgents' grip on the facility and to rescue security forces trapped inside it just outside the town of Baiji.
Two policemen were also killed, the security sources said.
"The general was in his Humvee with two of his men. A suicide bomber in a truck targeted him directly," said an officer under his command.
Iraqi security forces have repeatedly tried to push Islamic State fighters out of the refinery compound, where security forces have been surviving on airdrops.
The death of Malik came after Iraqi security tried a new strategy to break the Islamic State siege of the refinery near Baiji, which lies 200 km (130 miles) north of Baghdad.