A leading Islamic advocacy group called for an investigation after six imams were removed from a US Airways flight and detained, due to what the group suspected was persistent "fear and prejudice" against Muslims.

The imams were among the passengers who boarded Phoenix-bound Flight 300 in Minneapolis, and had been attending a conference of the North American Imams Federation. They were removed Monday evening after three of them recited their evening prayers in the airport terminal before boarding the plane, a leader of the group said.

"We call on relevant authorities to investigate whether proper procedures were followed by security personnel and members of the US Airways flight crew," said Nihad Awad, executive director of the Washington-based Council on American Islamic Relations.

"We are concerned that crew members, passengers and security personnel may have succumbed to fear and prejudice based on stereotyping of Muslims and Islam," he said.

A passenger initially raised concerns about the group through a note passed to a flight attendant, according to Andrea Rader, a spokeswoman for US Airways. She said police were called after the captain and airport security workers asked the men to leave the plane and the men refused.

"They took us off the plane, humiliated us in a very disrespectful way," said Omar Shahin, one of the six clerics. Shahin and four of the others are from the Phoenix-Tempe area while the sixth is from Bakersfield, California.

Shahin attributed any concerns by passengers or crew to ignorance about Islam.

"I never felt bad in my life like that," he said. "I never. Six imams. Six leaders in this country. Six scholars in handcuffs. It's terrible."

CAIR planned a news conference Tuesday in Phoenix in which it said it would call on authorities to investigate the incident.

The clerics told CAIR they suspected the "suspicious activity" cited by authorities was the performance of normal evening prayers, according to a statement by the advocacy group.

The clerics also denied that they refused to leave the plane or that they chanted "Allah," the Arabic word for God, as they were escorted from the flight, said CAIR.

Public prayer is not a threat to safety or security and should not be viewed as suspicious or criminal activity, said the statement by CAIR.

Ibrahim Hooper, CAIR's spokesman, said the conference which the clerics attended drew about 150 imams from all over the country, and that those attending included Democratic U.S. Rep.-elect Keith Ellison, who just became the first Muslim elected to Congress.

Shahin said they went as far as notifying police and the FBI about their meeting in advance. He also expressed frustration that, despite efforts by him and other Muslim leaders since even before the Sept. 11 terrorist attacks, that so many American know so little about Islam.

"If up to now they don't know about prayers, this is a real problem," he said.

Shahin said Tuesday that the group spent Monday night in the Minneapolis area at the home of a local imam. Hooper said US Airways refused to put the men on another flight.

Hogan said more information would likely be released Tuesday.

The other passengers on the flight, which was carrying 141 passengers and five crew members, were re-screened for boarding, Rader said. The plane took off about three hours after the men were removed from the flight.