The crudely made anti-Muslim video that has sparked violent outrage in Egypt and Libya this week was posted prominently Monday on the Web site of a Coptic Christian group headed by a Morris Sadek, an Egyptian American activist and lawyer who lives in Northern Virginia.

The site features a grainy photo of two actors in white turbans, the title “English Muhammad Movie Trailer” and a link to the video on YouTube. Next comes an ad for “International Judge Muhammad Day” on Sept. 11, questioning whether the prophet Muhammad was a “pedophile” and a “deceiver,” and a photograph of Sadek shaking hands with rightist Florida pastor Terry Jones.

Coptic Christian leaders in the Washington region and across the United States have denounced the video as highly offensive and inflammatory, and they have expressed concerns that it could further inflame Muslim sentiment against Copts in Egypt, where the large Christian minority has faced harassment and violence for years.

Federal authorities on Thursday said that a Coptic Christian man in southern California, currently on probation for financial crimes, is the key figure behind the video. According to the Associated Press, government sources said that Nakoula Bassely Nakoula, 55, was the person who wrote and directed the film.

In a statement Thursday, the senior Coptic Orthodox bishop in Los Angeles said the church “strongly rejects dragging the respectable Copts of the diaspora” into the controversy over the film. “It is not the Christian way to respond to hatred with hate.”

But Sadek, who did not return e-mails or phone messages Thursday, appears to have played a role in promoting the video, which depicts Islam’s most revered figure as a vulgar, violent womanizer swaggering in the desert with a gang of thugs. The video provoked violence Wednesday, including an assault on the U.S. Consulate in Libya that killed Ambassador J. Christopher Stevens.

Sadek posted the U.S.-made video, with Arabic subtitles, on the Web site of the National American Coptic Assembly, a group he heads that is based in Chantilly. Several Coptic activists also said he sent e-mails promoting the video to hundreds of people, including local followers and journalists in Egypt. However, they said that they did not believe Sadek had played a role in adding the subtitles.

Sadek’s autobiography on the Web site describes him as a lawyer and human rights activist who was born in Egypt in 1942 and now lives in the United States. It includes a lengthy resume of academic degrees, awards, bar association memberships in both countries, conferences attended and published works. It describes him as a longtime legal defender of religious freedom in Egypt with offices in Fairfax County.

Some religious activists in the Washington area said they had seen Sadek at conferences and meetings over the years, but they described him as a fringe figure whose rhetoric was stridently anti-Islamic. Coptic activists here said that he has been rejected by organized local Coptic groups but that he regularly sends out provocative e-mails attacking Islam.

They also said that Sadek had been interviewed by phone on television and radio in Egypt this week in connection with the video, and that his e-mails are regularly sent to newspaper editors and opinion makers in Egypt. They added that he had peppered Western and Israeli leaders with letters demanding they act against Egypt.

“He just wants to keep insulting Islam. He does not represent Copts, and we have excluded him from all our activities,” said Magdi Khalil, an activist with the rights group Coptic Solidarity who is based in Virginia. Khalil said that he is on Sadek’s e-mail list and that Sadek sends “very hateful messages. I am totally against what he has done.”

Sadek’s Web site says he is affiliated with a legal aid group called Advocates International in Northern Virginia. The group’s president, Brent McBurney, said Thursday that it had once helped Sadek with human rights cases in Egypt but had not had any contact with him in the past 10 years.

Mohamed Elmenshawy, an Egyptian scholar and journalist at the Middle East Institute in Washington, said that he had seen Sadek occasionally at conferences and public events and that he had become “a kind of celebrity” in some sectors of the Egyptian media because of his provocative and extreme comments.

“A film like this gives the radicals in Egypt more publicity than they ever dreamed of, because it was made by radicals on the other side,” Elmenshawy said. “They are both a tiny minority, but they have very loud voices.” He criticized Sadek for promoting a film that could make things worse for his fellow Copts in Egypt, where it is being portrayed as “the work of Copts in America.”

So far, Sadek appears to be the only American Copt who has publicly promoted the video. It is not known if he has any connection to Nakoula.

In the Washington area, home to several thousand Egyptian Coptic immigrants, many are educated professionals who profess strong beliefs in religious tolerance.

“What happened this week was totally senseless and tragic. All of us Copts have been in touch with each other, and we all agree,” said Halim Meawad, a founder of Coptic Solidarity and a retired U.S. diplomat who lives in Virginia. He denounced the video as “insulting to every Muslim” but also said the attack that killed Stevens “affected me very personally. I was a Foreign Service officer, too. It is so very, very sad.”