A US Army major firing two handguns killed 11 people and wounded 31 others in a shooting rampage on Thursday at Fort Hood base in Texas, a prime point of deployment for US operations in Iraq and Afghanistan.

The Army said the gunman was killed. US broadcast media identified him as Major Malik Nidal Hasan, and said he was a psychiatrist who was facing an upcoming deployment to Iraq.

There was no immediate official confirmation of his identity.

US Senator Kay Bailey Hutchison of Texas told Fox News:  "I do know that he has been known to have told people that he was upset about going (to Iraq)." US military officials say the shooter's motives were still unclear.   

The incident at Fort Hood, the largest military installation in the world, was one of the worst killings reported on a US military base. In May a US soldier at a base in Baghdad shot dead five fellow soldiers.

It raised new questions about the toll that six years of continuous fighting in Iraq and nearly eight years fighting in Afghanistan have taken on the US military and on individual soldiers, many of whom have been on several combat tours.

In Thursday's incident, the shooter opened fire at about 1:30 pm CST (1930 GMT) at the Soldiers Readiness Processing Center, where soldiers were getting medical check-ups before leaving for overseas deployments, the Army said.

The shooter was killed by police, but not before he killed one civilian police officer, Cone said.

Initial reports said two other soldiers had been detained as possible suspects.

US President Barack Obama called the event a "horrific outburst of violence" and promised "answers to every single question about this horrible incident."    

"It is difficult enough when we lose these brave Americans in battles overseas. It is horrifying that they should come under fire at an army base on American soil," Obama said during an event in Washington.

Fort Hood is home to about 50,000 troops, although Senator Hutchison said only about 35,000 were on base at this time. -Reuters