At least 12 people have been killed and as many as 31 wounded at an army base in Texas after gunmen opened fire.

The killer, believed to be a member of the US army, was shot dead at the scene. Two other suspects have been arrested in relation to the incident at Fort Hood.

The Associated Press news agency named the suspected killer as Major Malik Nadal Hasan. Unconfirmed reports tonight said he was due to be deployed to Iraq.

An army spokesman said 11 soldiers and one civilian policeman were among the victims.

Barack Obama, the US president, called the incident “a horrific outburst of violence”.

The shootings took place about 30 minutes before a scheduled graduation event involving universities located on the base, 50 miles south of Waco.

The assailant entered the base’s readiness centre – where soldiers about to be deployed or just returning from action undergo medical checks – armed with two handguns.

After the initial attack, two other soldiers acting suspiciously were picked up at a separate location within the complex, army spokesman Lt Gen Robert Cone said.

Army officials said it was too early to speculate on any motive.

The incident comes at a time when the US army is suffering an increase in suicides and stress-related disorders.

Fort Hood is a sprawling 340 square mile military installation and houses some 4,929 active duty officers and 45,414 enlisted members of the army.

Domestic killings are not normally relayed to the president but his advisers opted to tell him because a military base was involved.

In brief remarks given after speaking with senior military personnel, the president said: “We do not know all the details at this moment.

“What we do know is that a number of American soldiers have been killed and even more have been injured in a horrific outburst of violence.”