An Iraqi Trade Ministry media adviser killed last month by a bomb attached to his car had been about to hand over files accusing the ministry of corruption to the country's Integrity Commission, officials in the ministry's legal department told Reuters.

Baghdad's Central Investigative Court for Terrorism and Organised Crime said in a statement that four Trade Ministry security guards confessed to blowing up Trade Minister Milas Mohammed Abdul Kareem's media adviser, Nadhim Naeem.

A spokesman for that court said the men, arrested for killing several trade ministry employees including Naeem, were part of Abdul Kareem's protection unit. They are awaiting trial on charges of terrorism and premeditated murder, he said.

Abdul Kareem was not immediately available for comment, and neither were his bodyguards.

There is no evidence implicating Abdul Kareem in the killing and he was cleared in an investigation ordered by Prime Minister Haider al-Abadi.

Despite absolving Abdul Kareem of murder, Iraq issued an arrest warrant for the minister and his brother on Oct. 18 after a corruption investigation into bribes, illegal benefits, and the misuse of his position.

Abdul Kareem issued a statement on the Trade Ministry website saying the warrants were not based on solid evidence of wrongdoing related to ministry contracts.

Abadi has promised to tackle corruption in a political system which doles out positions along ethnic and sectarian lines, creating powerful patronage networks.

Abdul Kareem is among the most senior officials to face judicial action since Abadi announced his crackdown in August after nationwide protests erupted over corruption, poor electricity and water services and unemployment.

TEST OF ABADI'S RESOLVE

His first big test could be the corruption allegations and murder case hanging over one of Iraq's most critical ministries, responsible for purchasing billions of dollars worth of commodities used in a nationwide ration program.

Iraq is one of the world's biggest importers of wheat and rice. Several Trade Ministry officials have faced corruption allegations in the past.

Two officials in the Trade Ministry's legal department said Naeem had spoken out to them and other colleagues in the ministry about corruption and his intention to hand over files to the Integrity Commission, Iraq's highest state-run corruption watchdog.

"He said he will not stay silent about corruption in the ministry. He crossed a red line and spoke out against corruption in the ministry," one of the officials told Reuters.

The other Trade Ministry legal department official said Naeem had put himself in danger.

"He repeated so many times that he will never hesitate to reach the Integrity Commission to inform about corruption cases in the ministry. We knew he became inside the circle of danger. His end was tragic," he told Reuters.

According to police and ministry officials, CCTV footage showed some of the minister's bodyguards attaching a bomb to the car used by Naeem.

"A network of four security employees from the Trade Ministry protection were arrested for carrying out terrorist actions. The group confessed to carrying out a number of assassinations against employees in the Ministry," according to a statement by the Baghdad criminal court.

"The confessions were supported by video footage showing the assassination of the media man Nadhim Naeem who was working in the same ministry. The assassination was carried out by a bomb attached to his vehicle," the statement added.

WHITE LAND CRUISER

The footage, carried on YouTube and seen by Reuters, shows a white Toyota Land Cruiser, the kind of vehicle often used by senior ministry officials and their guards, pulling up to Naeem's car in the ministry outdoor parking lot.

Two men are seen standing beside the car and moving around. Naeem then drives away and is later blown up. Reuters could not verify the identity of the men in the video or if they actually had made confessions.

Although Abdul Kareem was not implicated in the murder, officials said the murder case triggered a wider investigation by the courts into corruption related to the purchase of commodities and construction equipment that resulted in arrest warrants for Abdul Kareem and his brother.

A court also summoned Abdul Kareem and eight other ministry officials, including the head of the grain board responsible for procuring Iraq's grain internationally and from local farmers.

They were questioned over alleged illicit gains made from the purchase of a Uruguayan rice shipment which was seized because it was unfit for human consumption, according to Baghdad's Integrity Investigation court.

The Trade Ministry official, who is close to Abdul Kareem, said he should not be blamed for the corrupted rice shipment because the problem was due to poor storage facilities.

"This does not merit an arrest warrant for someone as senior as the minister, especially because the contract was legal and based on global prices," he said.

Asked about charges against Abdul Kareem's bodyguards, he said "justice should take its course".

(Writing by Michael Georgy, editing by Timothy Heritage and Peter Millership)