On the main road through Mahmudiya, being recognised as a foreigner has become a matter of life and death.
Local doctors spelt this out when they urged me to cover my head on leaving the hospital in the town, 15 miles south of Baghdad.
The death of an American missionary on the dusty road south of the town has unnerved foreigners and the Iraqis who deal with them.
Plenty of foreigners have died in Iraq, but the road through Mahmudiya has become the scene for a new type of killing: drive-by shootings in which foreign civilians are the targets.
The death of the Rev John Kelley, a Baptist missionary from Rhode Island, on Saturday, has set alarm bells ringing for several reasons. For one, it revealed that American missionaries were inside Iraq trying to set up new churches and, presumably, find converts.
That will be deeply offensive to the vast majority of Iraqis, who are Muslims. The unwelcome presence of the missionaries could become a new source of friction between Iraqis and their already deeply unpopular American occupiers.
If Mr Kelley's death were an isolated incident, it would be easy to assume that he and his colleagues were deliberately tracked down. But it was the second incident of its type on the road, and in the first it was foreign journalists and the Iraqis working with them who were the targets. Two Iraqis working for the American network CNN were killed when the two-car convoy they were travelling in came under fire near the town a few weeks ago.
After the two ambushes, foreign journalists and aid workers became nervous about taking the road through Mahmudiya, the main route south to the Shia holy cities of Najaf and Kerbala. Ten months into the American occupation, the roads of Iraq are becoming more dangerous.
Doctors at Mahmudiya hospital said yesterday that a taxi drove to the front gate on Saturday with all its windows shattered and a passenger in the front dead in his seat. "The driver was screaming 'Help me. Help me'," said a doctor who would not give his name.
The dead man was Mr Kelley. In the back of the taxi were three other American missionaries: the Rev Kirk DiVietro, the Rev David Davis and a fourth whose identity is not known. Though their injuries were slight, they were too terrified to get out of the taxi until doctors had calmed them.
The taxi driver told hospital staff that the group was on the outskirts of Mahmudiya heading north to Baghdad after a visit to ancient Babylon. A red Opel started overtaking on the inside and those inside opened fire on the taxi. There were four people in the Opel armed with Kalashnikovs, the taxi driver said.
The doctors denied American reports that the injured men had been found by chance at the hospital by a routine American patrol. They said that they had informed the Iraqi police, who had passed on the details to American soldiers stationed in Mahmudiya. "It is our responsibility to help injured people," said one.
The four missionaries were on their way back to their hotel in Baghdad. They probably travelled without bodyguards in the belief that, as civilians, they would not be targets for Iraqi gunmen.
Until recently, relatively few foreign civilians have been attacked travelling on their own in Iraq. Attacks on foreign civilians have been aimed at large targets, such as the bombings of the UN and Red Cross in Baghdad. But the nature of their work in Iraq meant that the missionaries were putting themselves in danger.
Although it is a Sunni town, Mahmudiya lies outside the so-called Sunni Triangle where most resistance attacks began. But the resistance has spread far beyond that area now.
One doctor said: "Fallujah may be the symbol of the resistance, but we have more attacks on the Americans in Mahmudiya now. You should stay here. You will see plenty of incidents, I promise you."
The Mahmudiya road has become renowned for attacks on American military convoys. After this attack, foreign civilians may soon start avoiding the road altogether.