Arab-Americans have come forward to donate blood
There are reports of a shooting at a Texas mosque, threatening phone calls to Arab-American groups, and hate messages on Internet sites.
New York Mayor Rudolph Giuliani has promised police protection for neighbourhoods with large numbers of Arab-Americans.
Mosques and Islamic centres in other cities were placed under 24-hour police guard.
Double tragedy
President of the Arab American Institute Dr James Zogby told BBC News Online it had been a trauma for all Americans, including Arab-Americans, many of whom had lost friends and relatives in the disaster.
"Arab-Americans are as afraid, grieving and mourning as everyone else. But for us it's a double tragedy, because while we grieve, we're forced to look over our shoulder."
Dr Zogby said he had received several death threats and was arranging security for his office.
"I take such threats seriously since my office was fire-bombed in 1980," he said.
Pearl Harbour
"Regardless of who is ultimately found to be responsible for these terrorist murders, no ethnic or religious community should be treated as suspect and collectively blamed," the Arab American Institute, based in Washington, said.
Chairman of the Arab-American Business and Professional Association in Washington, Fuad Sahouri, drew the parallel with what happened to Japanese-Americans in the wake of the attack on Pearl Harbour, to which Tuesday's attacks have been frequently compared.
"We don't want to be excluded or insulated or treated how Japanese-Americans were treated," he said.
"It's very important right now for Arab-Americans that their loyalty never be brought into question."
"We are Americans first."
Arab roots
There are thought to be around three million US inhabitants who have roots in the Arab world.
Of these, the largest community is in Los Angeles, but the most influential group live in the Detroit and Dearborn area of Michigan, where about 300,000 Muslims live.
Arab-Americans are thought to have voted heavily in favour of George W Bush in the presidential election.
Their most prominent political representative is the former Republican senator for Michigan, Spencer Abraham.
Mr Abraham is now President Bush's Energy Secretary.