The officer in question, who worked for the intelligence, was investigating targeted killings of activists, a security source who spoke on condition of anonymity told AFP.

At least four civilians were killed and four others wounded in Tuesday's motorcycle bombing near a hospital in central Basra. The attack has not been claimed.

"Yesterday, we witnessed an attempt to assassinate an officer in Basra because he was searching for the criminals and death squads," Kadhemi said.

Since protests broke out across much of Iraq in October 2019 over rampant corruption and high unemployment rates, dozens of activists and protesters have been targeted in assassinations or attempted killings, while others were briefly abducted.

The government, led by Kadhemi who took office in May 2020, has repeatedly vowed to track down the perpetrators.

On Wednesday, Kadhemi said the killers of security adviser and researcher Hisham al-Hashemi, who was shot near his home in July 2020, were now "in prison awaiting justice".

"We salute the courageous judges in the city of Basra who were not terrorised by the blackmail and intimidation of groups and death squads," he added.

In early November, a court in Basra sentenced two people to death over the killing of a teenager who took part in protests last year.

Days earlier, the same court had sentenced another man to death over the killing of two journalists covering the demonstrations in Basra in January 2020.