FOUR people are dead and at least 11 others wounded after a shooting incident at the Fort Hood military base in Texas.

The suspected shooter, identified as Ivan Lopez, a 34-year-old enlisted soldier, was thought to be among the dead.

The base, which is near Waco in central Texas, is home to the US Army's 1st Cavalry Division, and was also the site of a 2009 mass shooting in which 13 people were killed.

According to witnesses and military officials, the shots rang out at around 4.30pm local time.

The base's emergency sirens sounded, and the facility was immediately put on lockdown as law enforcement and emergency services personnel scrambled to the scene.

Officials said the gunman had died from a self-inflicted gunshot wound.

A Department of Homeland Security source told Fox News that the shooting was a "soldier on soldier" incident arising from a personal dispute, and that terrorism was not a factor. Several other people were rushed to nearby hospitals in critical condition.

Three later died and doctors said a fourth was in extremely critical condition at Scott & White Memorial Hospital in Temple on Wednesday evening.

The events come just months after the trial of Major Nidal Malik Hasan, a radicalised Muslim-American army psychiatrist, who opened fire at a soldier readiness centre at Fort Hood on 5 November, 2009, shooting dead 13 people and wounding 32 others.

That was the worst shooting ever to occur on a US military base. At the time of his rampage, Hasan was shot by police and paralysed. In August 2013, he was convicted of the killings and sentenced to death.

Speaking to reporters in Chicago shortly after news of the shooting broke, President Barack Obama said: "We're heartbroken something like this might have happened again."

Shooter killed after Fort Hood military base goes into lockdown

10.30AM: IT IS believed up to four are dead after a shooting at Fort Hood military base in Texas.

The Washington Post is reporting sources saying four are dead from the incident, including the shooter.

The shooter has been identified by multiple government sources as Army Specialist Ivan Lopez, the Post reported.

There are believed to be 14 people injured in the shooting, according to law enforcement officials.

A US law enforcement official said reports circulating within the Justice Department indicate the shooter died of what appears to be a self-inflicted wound. 

The Army said on its official Twitter feed that the Texas Army post was still on lockdown.

9.30am: A GUNMAN  has opened fire at the Fort Hood military base this morning, killing one person and injuring 14 others, according to senior US defence official.

The Bell's County Sheriff's Office dispatched deputies and troopers from the Texas Department of Public Safety to the base after receiving reports of an "active shooter," sheriff's Lieutenant Donnie Adams said.

FBI spokeswoman Michelle Lee said its agents were also headed to the scene.

The base was the scene of a mass shooting in 2009, when 13 people were killed and more than 30 wounded.

White House spokesman Josh Earnest said the president has been informed of the reports of a shooting at Fort Hood and will continue to receive updates as he attends a pair of Democratic Party fundraisers in Chicago.

A witness told News 10 that about 20 shots were fired during the incident this morning.

Just after 9am, Queensland time, there were reports one of two possible gunmen had died from gunshot wounds.

KCEN TV said a suspect was still at large and was thought to be in a medical building in the base.

The military base had been placed on lockdown.

Fort Hood has ordered everyone on site to "shelter in place."

The order was sent on the base's Twitter feed and posted on its Facebook page.

A witness told US television that there were 18 ambulances on the scene, dozens of police vehicles as well as a police helicopter flying overhead.

He said SWAT police were arriving on the scene.

As he was reporting there were another three ambulances arriving.

Later the witness, named only as Tyler, said there were a group of men, women and children being escorted out of the base by armed military personnel.

They were being released.

"I think they were evacuating the building for safety,'' he said.

CNN was reporting that one shooter was at large and another was in custody.

KCEN TV said the suspect was thought to be in a medical building in the base.

Latest updates from NZ Herald here

Reports of multiple shootings at Fort Hood

Earlier, CEN-TV in Central Texas reported multiple people have been injured today in a shooting at Fort Hood.

A U.S. Army official at Fort Hood confirmed that a shooting has occurred at Fort Hood, though the number of people injured remains a mystery.

KCEN reports at least one person has been transported to an area hospital in an unknown condition and that an unknown number of others are injured.

The shooting is believed to have taken place at the Medical Brigade Building.  KCEN-TV reports there are also reports of victims at the Battle Simulation Center.

The shooter is believed to be at-large and the base is on lock down.  Just after 5 p.m., the base tweeted that all personnel are being asked to shelter in place.

In November 2009, 13 people were killed and more than 30 others injured when Maj. Nidal Hasan opened fire on dozens of people at the base.

Hasan was paralysed during an exchange of gunfire and, in late 2013, was sentenced to death.  He is currently awaiting execution.

More on this story from US TV