By Andrea Shalal-Esa

WASHINGTON (Reuters) - Arab and Muslim Americans on Friday braced for the possibility of verbal or physical attacks after an Army psychiatrist of Arab descent allegedly killed 13 during a shooting rampage at a military base in Texas.

Suspected gunman Major Nidal Malik Hasan opened fire with two handguns at the Fort Hood Army post on Thursday, in one of the worst killing sprees ever reported on a U.S. military base, army officials said.

The U.S.-born son of Palestinian immigrants, Hasan's Muslim and Arab heritage prompted immediate speculation on television stations and Internet sites about his motives and whether they were influenced by his background.

Andrew Grant-Thomas, deputy director of the Kirwan Institute for the Study of Race and Ethnicity at Ohio State University, said reporting about the incident had unduly emphasized Hasan's ethnicity and religion.

He also said some politicians were using the incident to fan fears about Islamic extremism, citing a statement by retired Army Lieutenant Colonel Allen West, who is running for Congress in Florida, that urged the Pentagon to do a better job to prevent Muslim extremists from "infiltrating" its ranks.

Some Arab and Muslim groups said they feared a backlash, although a Justice Department spokesman said its civil rights division was unaware of any incidents of violence directed against Arab-Americans or Muslim-Americans since the shooting.

U.S. Arab and Muslim groups condemned the shootings, offered condolences to the victims' families, and stressed that no political or religious ideology justified such violence.

Hate crimes against Arab Americans, Muslims, and Sikhs rose after the September 11, 2001 attacks. The number has since declined but many Arab and Muslim Americans still report verbal abuse and harassment. Continued...