Two gunmen shot and killed a senior Baath party official who appeared regularly in uniform on Iraqi state television singing anthems praising former Iraqi president Saddam Hussein.
It was one of the first known revenge murders since the fall of the regime.
Daoud al-Qaisy was a familiar face in the dictator's relentless propaganda machine through his television appearances. At dusk on Saturday, gunmen drew up outside his large house in central Baghdad and shot him dead on his doorstep.
Similar attacks on the party's leaders have been reported from other areas, including an attack earlier this month in a Shia district formerly known as Saddam City, where a Baathist and several members of his family were killed.
Many Iraqis had long expected the fall of the regime to trigger a wave of brutal lynchings. For many it has come as a surprise that it took so long for the attacks to begin.
The murder on Saturday, which was committed less than two miles from a US military patrol, underscores the sense of lawlessness that has gripped the capital.
On Monday, thousands of protesters marched to the Kadhimiya mosque in northwestern Baghdad, in the biggest demonstration so far against the US military.
Many in the crowd were followers of some of the hardline Shia clerics who have begun to emerge as popular figures. They also criticised the lack of security in Baghdad, the shortage of electricity and the slow pace of reconstruction.
Graffiti has begun to appear on street corners in Baghdad threatening attacks on American soldiers. "You'll be dead US army," reads one message in English.
Al-Qaisy had the relatively senior rank of "comrade" in the Baathist hierarchy and was handed military command of seven districts in his area of Baghdad.
By profession, he was a singer and the head of the Iraqi artists' union, where he was responsible for keeping the propaganda flowing.
The gunmen drove up to the house in a Nissan pick-up truck, he said. One of them called his father to the door, started talking to him and then shot him in the head.
A bullet found in the kitchen wall after the attack revealed that the killer had used a .38 revolver, a gun commonly available in the city.
The singer was injured in an assassination attempt during an uprising after the 1991 Gulf war. He survived, despite being shot five times.
In the run-up to the recent war, he fled his home and was sheltered by his sister. Two weeks ago, he returned to his Baghdad house. "He was scared and he knew his life could be in danger. This was an organised killing," his son said.
US officials said last week that up to 30,000 Baathists would be permanently excluded from future governments in Iraq.
Salwan said that the announcement would trigger more attacks.