Portland Mayor Sam Adams said Sunday that he beefed up protection around mosques "and other facilities that might be vulnerable to knuckle-headed retribution" after hearing of the bomb plot.
Mohamud, 19, was being held on charges of plotting to carry out a terror attack Friday on a crowd of thousands at Portland's Pioneer Courthouse Square. He is scheduled to appear in court Monday afternoon.
His attorney, Stephen R. Sady, who has represented terrorism suspects held at the U.S. prison at Guantanamo Bay, didn't return a telephone message left Sunday by The Associated Press.
The suspect's mother, Maryan Hassan, declined to discuss the issue when contacted by phone late Sunday by the AP, referring all questions to Sady. His father also refused to comment.
Somali leaders in Oregon - a state that has been largely accepting of Muslims - gathered with Portland city leaders Sunday evening to denounce violence and call for help for at-risk Somali youth.
"We left Somalia because of war, and we would like to live in peace as part of the American community," said Kayse Jama, executive director of a local organization founded after the 9/11 attacks to fight anti-Muslim sentiment. "We are Portlanders. We are Oregonians. We are Americans, and we would like to be treated that way. We are your co-workers, your neighbors."
Earlier Sunday, worshippers at the damaged Islamic center expressed concern about retribution.
"I've prayed for my family and friends, because obviously if someone was deliberate enough to do this, what's to stop them from coming to our homes and our schools?" said Mohamed Alyagouri, a 31-year-old father of two who worships at the center. "I'm afraid for my children getting harassed from their teachers, maybe from their friends."
Yosof Wanly, the center's imam, said he was thinking about temporarily relocating his family because of the possibility of hate crimes.
"We know how it is, we know some people due to ignorance are going to perceive of these things and hold most Muslims accountable," Wanly said. But he said Corvallis has long been accepting of Muslims.
Omar Jamal, first secretary for the Somali mission to the United Nations in New York City, told The Associated Press his office has received "thousands of calls" from Somalis in the United States who are concerned about tactics used by federal agents in the sting operation against Mohamud.
An FBI affidavit said agents began investigating after receiving a tip from an unidentified person who expressed concern about Mohamud.
An agent e-mailed Mohamud, pretending to be affiliated with one of the people overseas whom Mohamud had tried to contact. Undercover agents then set up a series of face-to-face meetings with Mohamud at hotels in Portland and Corvallis.
Authorities said they allowed the plot to proceed to obtain evidence to charge the suspect with attempted use of a weapon of mass destruction.
Jamal said there is concern in the Somali community that Mohamud was "lured into an illegal act."
"Rest assured that the community is very against anyone who tries to do harm to the citizens of this country," he said. But many Somalis in the United States are wondering whether Mohammud's rights were violated by federal agents, he said.
Why "did they tell him to go along with this heinous crime?" Jamal said.