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 the country's biggest refinery for months, security sources said.
The attack killed general Faisal Malik, one of the supervisors of the operation designed to break the Sunni insurgents' grip on the facility and rescue security forces trapped inside it just outside the town of Baiji.
Two policemen were also killed.
Also on Friday, Iraq's most influential Shi'ite cleric said that corruption in the armed forces enabled Islamic State to seize much of northern Iraq, criticism that will pressure the government to enact reforms in the face of an insurgency.
Grand Ayatollah Ali al-Sistani has become increasingly critical of Iraqi leaders since Islamic State's lightning advance, which created Iraq's worst crisis since a U.S.-led invasion toppled Saddam Hussein in 2003.
Iraq's army, the recipient of $25 billion in U.S. training and funding, collapsed in the face of the onslaught. Further Islamic State advances and the beheading of Western hostages triggered U.S.-led airstrikes.
Speaking on live television through an aide, Sayyid Ahmed Al-Safi, in the holy southern city of Kerbala, Sistani asked what would happen if the military was corrupt.
"Military and security forces are directly responsible for protecting the country against any inside and outside threats to its people and they are responsible for protecting the country's other institutions and keep them away from any political influence, so, what would happen if the military was not far from corruption?" he said.
"We think that the security deterioration which happened some months ago can answer that. Objectivity demands that the different military positions should be occupied by those who are professional, nationalist, faithful, courageous and not affected in doing their duties with personal and financial influences. As we greet our faithful sons in the armed forces, and truly there are many, we hope that the problems that undermine this institution might be addressed and that all the aspects of corruption terminated, even if petty, because petty corruption can be damaging," he added.
Sistani, 84, is a reclusive figure and always delivers his public messages via a proxy.
The cleric has openly criticized Iraqi leaders and politicians, saying their bickering and sectarian differences were undermining Iraq, a major OPEC oil producer.
The comments about the army mark a deeper level of concern over the stability of Iraq.
U.S. airstrikes have prevented Islamic State from making further large-scale advances since August, when the al Qaeda offshoot humiliated Kurdish peshmerga forces in the north and triggered a massive exodus of minority communities.
Lacking a strong army, Iraq's government turned to Iranian-backed Shi'ite militias for help. But their alleged violations of human rights have deepened sectarian tensions, with the Sunni minority complaining of kidnappings, torture and executions.
Militia leaders deny those accusations and say their fighters are hunting Islamic State fighters who hide in Sunni communities.
Britain will boost the number of its army trainers in Iraq in the coming weeks to support the Iraqi armed forces' battle against Islamic State militants, the British defense secretary said on a visit to Baghdad on Wednesday.
Michael Fallon, who met top Iraqi government officials during his visit to Baghdad, said the details of the mission would be ironed out soon.
Even if more Western countries step up support for Iraq's military, the overriding question will be can the Shi'ite-led government revive al alliance with Sunni tribesmen who helped defeat al Qaeda during the U.S. occupation?
Leaders of Anbar Province's Albu Nimr tribe, which suffered the massacres of hundreds of its members over the past two weeks, say the Baghdad government and military ignored repeated please for help as Islamic State closed in on them.
REUTERS