SAN ANTONIO, Texas (AFP) - Up to three gunmen who opened fire Thursday on a US military base, killing 11 people and wounding 31 others, were all American soldiers, the Fort Hood commander said.

"A shooter opened fire. That person was killed. At this time, we are looking at 12 dead and 31 wounded. They are dispersed among the local hospitals in this area in Texas," said Lieutenant General Bob Cone.

The shooter was counted among the 12 dead.

"The shooter was killed. He was a soldier. We since then have apprehended two additional soldiers who are suspects, and I would go into the point that there were eyewitness accounts that there may have been more than one shooter."