Speaking at a State Department forum in 1999, Muhammad Hisham Kabbani, a Sufi sheik and leader of the Islamic Supreme Council of America, sounded an alarm about Muslim houses of worship in the United States.

"The most dangerous thing that is going on now in these mosques . . . is the extremists' ideology," he said. "Because they are very active, they took over the mosques; . . . they took over more than 80 percent of the mosques that have been established in the US." He warned ominously that "a danger might suddenly come that you are not looking for . . . we don't know where it is going to hit."

When Kabbani was condemned by other Muslim organizations, he stood his ground. His assessment of the leadership of US mosques, he said, was based on having visited scores of them. In a 2000 interview he explained the extremists' pattern of infiltration.

Muslim immigrants to the United States "came with a good heart . . . and they wanted a place to pray," Kabbani told the Middle East Quarterly. "They collected money and they built mosques in their community. Slowly, certain Middle Eastern groups seized these mosques, promoting political and ideological agendas rooted in their home countries' problems. . . . Slowly, such groups took over many mosques either directly or by unseen pressure on the moderate board members, and now an antagonistic mentality controls them. The extremists -- not ordinary believers -- changed the use of American mosques into centers of intolerant political dogma."

At the time, Kabbani's charges may have seemed little more than inside Muslim baseball. After Sept. 11, it became clear that mosques dominated by radical clerics were a potentially lethal threat. Many such mosques are funded by Saudi Arabia, which spends heavily to propagate Wahhabism, a fanatic and aggressive strain of Islam. The Saudi government, reported the 9/11 Commission, "uses zakat" -- Islamic charity -- "and government funds to spread Wahhabi beliefs throughout the world, including in mosques and schools. . . . Some Wahhabi-funded organizations have been exploited by extremists to further their goal of violent jihad against non-Muslims." Its findings were reinforced by Freedom House, which in 2005 documented the penetration of US mosques by Saudi-supplied Wahhabi hate literature.

It is against this background that the $24 million mosque and cultural center being built by the Islamic Society of Boston has generated such controversy.

Questions have been raised about the Islamic Society's past and present leaders, some of whom have supported Islamist terrorism or indulged in virulently anti-American and anti-Semitic rhetoric. There are concerns about the sweetheart deal in which the land for the mosque was acquired from the City of Boston for a fraction of its value. A devout Muslim scholar, Ahmed Mansour, examined the ISB’s library and found books and videos promoting "fanatical beliefs." Especially disturbing has been the Islamic Society's response to its diverse critics: a lawsuit accusing all of them -- even Mansour -- of anti-Muslim conspiracy and libel.

That libel, the lawsuit charges, included claims that the "ISB receives funds from Wahhabis and/or Muslim Brotherhood and/or other Saudi/Middle Eastern sources" and that "the ISB Project was supported financially by donors from Saudi Arabia and the Gulf states 'with known connections to radical Islamists.' " Given the Saudi role in disseminating jihadist fanaticism, it might indeed have been defamatory to falsely accuse the ISB of financial ties to Saudi Arabia.

But those ties are all too real.

According to financial documents supplied to The Boston Globe, major funding for the mosque is being provided by the Islamic Development Bank in Jeddah, Saudi Arabia. In December 2005, for example, two payments of approximately $250,000 each were wired from Jeddah to the Citizens Bank account of the mosque's general contractor in Boston. Messages confirming the payments were faxed from Jeddah to the Islamic Society of Boston on Dec. 19. Other documents suggest that subsequent payments have been made as well. Yesterday, the ISB for the first time acknowledged receiving $1 million in financing from the Saudi bank.

The Islamic Development Bank is a subsidiary of the Organization of the Islamic Conference, and each of the conference's 56 member nations are shareholders. But the largest shares are owned by Saudi Arabia, Libya, and Iran, which together control 48 percent of the bank's stock. Saudi Arabia, Libya, and Iran are also three of the world's foremost sponsors or incubators of terrorism. It is perhaps not surprising that the Islamic Development Bank, through its Al-Quds and Al-Aqsa funds, has become a leading funder of Palestinian suicide bombing, paying large financial subsidies to the families of terrorists.

The Islamic Society of Boston didn't return my calls, but its website notes that all donors are cross-checked against the government's terrorist watch list, and that funding is accepted only "with no strings attached." It notes too that it "rejects any interpretation of Islam that is considered fundamentalist, oppressive, radical, anti-Western, or anti-Semitic."

But questions remain. More questions will come. Suing the good people who ask them won't make the questions go away. Answering them candidly, on the other hand, just might.