The Bush administration has used tough language in denouncing violence against Arab-Americans, who the administration has said are as loyal and law-abiding as any Americans.

Monday's message was aimed at Muslims worldwide, whose support the president is trying to secure as the United States nears war, and Arab-Americans who have complained of growing discrimination.

As many as 350 complaints have been reported nationwide since the attacks that left more than 5,000 people missing or presumed dead. The complaints include reports of arson and verbal and physical abuse, including two possible hate-crime deaths, said members of the Washington-based Council on American-Islamic Relations, or CAIR, an Islamic civil-rights advocacy group.

One of those cases involves the death of a Pakistani man in Pleasant Grove, though Dallas police and the FBI have yet to label the incident as a hate crime.

During his brief remarks, Mr. Bush made special mention of Islamic women, who civil-rights groups say are particularly vulnerable to attacks because of the religious garb they wear. In Memphis, Tenn., on Sunday, one woman was badly beaten on her way to worship, CAIR members said.

"Moms who wear cover must not be intimidated in America," said Mr. Bush, who in accordance with Muslim religious tradition removed his shoes before he entered the mosque. "That's not the America I know. That's not the America I value."

Robert Mueller, director of the FBI, said his agency has initiated 40 hate-crime investigations involving attacks on Arab-Americans. U.S. authorities have focused their investigation of the terrorist attacks on Saudi-born militant Osama bin Laden and radical cells associated with him.

"I'll make it very clear: Vigilante attacks and threats against Arab-Americans will not be tolerated," Mr. Mueller said. "Though we are all saddened by the recent acts of terrorism against our nation, such acts of retaliation violate federal law and, more particularly, run counter to the very principles of equality and freedom upon which our nation was founded."

Additionally, Mr. Mueller called on "English-speaking individuals with professional-level proficiency in Arabic and Farsi" to enlist in the FBI and help in the massive investigation. The attack on the World Trade Center killed or injured people from dozens of countries. Among the victims are an undetermined number of Americans of Arab or South Asian descent.

Mr. Bush's visit to the Islamic center Monday was "just another reminder that everybody in this country is an immigrant here," said White House spokesman Ari Fleischer.

During the weekend, the House unanimously approved a nonbinding resolution condemning acts of "bigotry and violence" against Arab-Americans, Muslims and South Asians living in the United States.

Still, CAIR, which held a news conference to denounce the incidents before the president's visit to the Islamic center, said the administration's message was falling on deaf ears.

In Mesa, Ariz., a gunman killed a 49-year-old Sikh owner of a gas station. Sikhs are often mistaken for Muslims because they wear beards and turbans.

"Bigots are never brain surgeons," said Ibrahim Hooper, spokesman for CAIR.

In the Dallas area, three mosques were hit by bullets and homemade firebombs. In Seattle, a man carrying a weapon was arrested after trying to set fire to a mosque. In Houston, arson was reported at a Pakistani-owned tire store. In Huntington, N.Y., a Pakistani woman was run over in a parking lot. In Ohio and Indiana, vehicles traveling at 80 mph rammed through Islamic centers. And a bomb went off at the Islamic center in San Diego.

"We are all Americans, and we shouldn't be judged on looks, by the way we talk or by our last name," said Nihad Awad, CAIR's executive director. Referring to the population of Muslims across the United States, Mr. Awad added, "We don't want 7 million Muslims to go into hiding."