For years, few Cambodians have taken much notice of the bearded foreigners coming to pray at the simple, white-washed mosques dotted alongside the murky waters of the Mekong river.
In a country awash with outside organizations all doing their bit to rebuild a nation shattered by decades of civil war, Arabs do not raise eyebrows as they help Cambodia's ethnic Cham Muslims recover from the Khmer Rouge genocide.
That was, until last month, when the deeply impoverished nation and its population of a few hundred thousand "forgotten Muslims" became the latest front in the US war on terror.
Acting on intelligence gleaned from joint operations with the US, Cambodian police swooped on a Saudi-funded Om al-Qura school near the capital to arrest three foreigners with suspected links to militant Islam, possibly even Osama bin Laden.
An Egyptian, two Thais and a Cambodian are in a Phnom Penh jail, accused of being members of Jemaah Islamiah, the Southeast Asian militant group believed to be behind the bombings in Bali. More than 200 people, most of them young Western tourists, died in last October's blasts.
Nearly 50 people, including teachers at the 500-pupil school and their families, left the country as part of the crackdown.
The arrests and closure of the school have been a rude awakening for the Cham and Cambodian authorities, whose relaxed attitude towards their Muslim compatriots could be about to change.
"Khmer Islam is very peaceful and the people are innocent. What I am afraid of is the people from outside. We are going to have to have more inspections," said Minister of Cults and Religions Chea Savoeun.
Although a predominantly Buddhist country of about 13 million people, the haunting cry of the muezzin summoning the faithful to prayer across the lush green paddyfields has been a feature of Cambodian life for centuries.
Descendants of the ancient kingdom of Champa in what is now central Vietnam, the Cham migrated to Cambodia in the early 1800s to escape religious and cultural persecution.
On the shores of the great Tonle Sap lake and the banks of the Mekong, they continued their idiosyncratic form of Islam, still heavily influenced by ancient beliefs including Buddhism and tribal magic.
It is these beliefs, which deviate from the strict Islamic canon, that make Cambodia's Muslims a likely target for Islamic puritans from overseas, scholars say.
"In Cambodia ... religious activists from the Arab world are arriving with a new view on religion and they preach an austere Wahhabiyya version of Islam," said Bjorn Blengsli, a Norwegian anthropologist who recently spent 10 months with the Cham.
"These organizations want to purify Cham Islamic practice by getting rid of the many influences from Buddhism," he said.
As well as financing hajj pilgrimages to Mecca, Islamic aid organizations from countries such as Kuwait and Saudi Arabia have built schools and mosques for Cham children, who are otherwise too poor to afford schooling.
The number of Islamic schools in Cambodia has been increasing steadily since the early 1990s, when UN-brokered elections signalled the beginning of the end of nearly three decades of civil war that included the 1975 to 1979 reign of terror by the Khmer Rouge.
The Ministry of Cults and Religions has 210 registered mosques but says it has no means of tracking the number or background of Islamic teachers floating around the country.
With its porous borders and lack of any intelligence infrastructure, foreign countries, especially the US, are becoming extremely nervous that senior Jemaah Islamiah or al Qaeda members might have gone to ground in Cambodia's backwaters.
"There are only four things the Americans care about in Cambodia: Wahabis, Wahabis, Wahabis and the elections -- in that order," one non-American diplomat said.
Cambodia goes to the polls next month.
Whether teaching a strict form of Islam translates into propagating militancy remains to be seen. The four arrested men face probes by investigating judges, a process which could take six months.
What is sure is that the Cham now fear their peaceful universe is being shattered as they become possible targets for discrimination.
"I don't believe that they are involved in terrorism or al Qaeda. Om al-Qura came to help the Cham people in Cambodia," said Ahmad Yahya, a minister and Cambodia's most vocal Cham.
The outsiders who have built the mosques and schools and provided the Cham with their only link to the outside world are unlikely to be back in a hurry.
"Some foreigners used to come here to pray once in a while, from Thailand, Afghanistan, Pakistan and Bangladesh," said Lep Res, a wizened 76-year-old who lives in a tarpaulin tent in the shadow of a mosque in Phnom Penh.
"I think they were good people because they only taught us about good and bad. They did not try to tell us what to do. They were just teachers, but now I do not think they will come back," he said.