Their religion, Mandeanism, comes from the same general background as Judaism, Christianity and Islam.
They share many of the same prophets, but particularly honour John the Baptist.
This is a religion almost solely confined to Iraq, but since the US-led invasion in 2003, many Mandeans have fled the country and now more than half of them live outside its borders.
The refugees speak of kidnap, murder and attempts at forced conversion.
One woman, Ibtisam Sabah Habib, said there had always been some threats and pressure to convert to Islam, but under the previous Iraqi regime there had been limits.
“Now, there are no rules and no government,” she said, describing how an armed gang of Islamic extremists had got into her house, killed her father and stolen all their money.
“They would telephone us at home, threatening us and trying to convert us. Then they tried to kidnap me.
“It was our neighbours who saved me. They’re Muslims – not all Muslims threaten us. But the extremists are very strong now – our neighbours couldn’t protect us all the time.”
Ibtisam was speaking from the safety of Syria, where she has fled with her husband and children.
Mandeans have traditionally been protected under Islamic law, as believers in one god – like Jews and Christians.
But since the war in Iraq, they have found themselves targeted by Sunni and Shia Islamic extremists, and by criminal gangs who use religion to justify their attacks.
One leaflet which Mandeans said had been distributed to homes in Baghdad gave this warning to both them and Christians (who form another of Iraq’s minorities):
“Either you embrace Islam and enjoy safety and coexist amongst us, or leave our land and stop toying with our principles. Otherwise, the sword will be the judge between belief and blasphemy.”
“They don’t accept us,” said Madeha Miran Daftah, who fled to Syria after her son was murdered and his corpse mutilated by people claiming to have killed an unbeliever.
“We don’t know what to do now. We lost everything in Iraq. We used to feel it was our country, but things are different now.”
One of her surviving sons, 24-year-old Shawq, who was kidnapped and tortured, said he could not imagine ever returning home. “I just want to live, not die like my brothers.”
Another woman, Shada Hanal, said she used to work as a teacher until she was sacked for refusing to wear the Islamic headscarf. Then her brother-in-law was attacked in his shop.
“His attackers beat him up and stole everything,” said Shada.
“When we went to seek justice, the judge said the Muslims had the right to steal from us. He said we were a sin in the world.”
Individuals from all religious and ethnic groups are suffering criminal and religious violence in Iraq, but the United Nations Refugee Agency, UNHCR, has said Mandeans are particularly vulnerable.
“We’re very concerned about them,” said a UNHCR spokesman, Peter Kessler. “There is so much discrimination against them and even persecution, and the numbers coming out of Iraq have been enormous compared to their population there, which is so small.”
Mandeans have their own language – Mandean – which is from the same family as Arabic and Hebrew.
Their central religious ceremony is baptism in flowing water, first in childhood, then marriage and at any time an individual wants to be cleansed of sin or make a life change.
Just 13,000 Mandeans are now left inside Iraq.
As the community there shrinks and people seek refuge outside, becoming a thinly scattered diaspora, many people are worried that their religion may not survive.
Maajis Saeb, a Mandean priest, says there are not enough men of religion to serve the various diaspora communities.
Luay Zahran Habib, a researcher in Mandeanism, is even more pessimistic: “Mandeanism may be finished in a few years’ time if we’re not gathered together somewhere, because it will be difficult to find marriage partners and perform our ceremonies.
“It’s not that we want to leave Iraq for no reason. We just need a safe place.” BBC