The US soldier accused of killing 16 Afghan civilians during a shooting rampage was known to friends and family as "level-headed," his lawyers said Saturday as they planned to meet with him next week.

The suspect, identified as 38-year-old US Army Staff Sergeant Robert Bales, had served three combat tours in Iraq -- where he was wounded twice -- and was on his first deployment to Afghanistan at the time of the killings.

Whisked out of Afghanistan to Kuwait in the days after the attacks, Bales was transferred to Fort Leavenworth, Kansas on Friday, where US officials said he was being held in "pre-trial confinement."

The US Army said Bales was being kept in "special housing" in his own cell, but no details have been released on a trial or even the charges to be brought against him.

"Public reports that Sergeant Bales's supervisors, family and friends describe him as a level-headed, experienced soldier are consistent with information gathered by the defense team," his lawyers said in a statement, saying it was still "too early" to determine what caused the attack.

Civilian attorneys John Henry Browne and Emma Scanlan, along with detailed military defense counsel Major Thomas Hurley, indicated they planned to spend "several days" meeting with Bales next week.

"Sergeant Bales's family is stunned in the face of this tragedy, but they stand behind the man they know as a devoted husband, father and dedicated member of the armed services," they added.

Friends and neighbors also expressed disbelief, telling local media he was a trusted soldier.

Bales allegedly left his base in the southern province of Kandahar before sunrise on Sunday, entered a nearby Afghan village and opened fire, killing men, women and children.

One of the worst atrocities committed by US forces in Afghanistan since the US-led invasion over a decade ago, the incident plunged US-Afghan relations to an all-time low.

Ties were already badly damaged after Americans burnt Korans last month, sparking a wave of deadly anti-American protests, and an earlier video that showed US Marines urinating on the corpses of Taliban militants.

Several websites containing pictures and stories about Bales, including a 2009 Defense Department page, were taken down by the time his identity was revealed Friday, but some versions of the Web pages could still be accessed, shedding light on his military career.

According to a cached online article dated February 2009 from the official US Army website, Bales participated in one of the bloodiest clashes of the Iraq war -- a January 2007 battle against a messianic Shiite sect in southern Iraq known as the Soldiers of Heaven.

In the 15-hour engagement, according to the article, 250 fighters were killed, all enemy -- and Bales said he was proud his unit "discriminated between the bad guys and the noncombatants and then afterward we ended up helping the people that three or four hours before were trying to kill us."

"I think that's the real difference between being an American as opposed to being a bad guy, someone who puts his family in harm's way like that," Bales said.

Browne, the civilian attorney, said this week his client had gotten angry about a serious injury that a comrade sustained the day before the massacre, but held no animosity toward Muslims.

Bales, who joined the army less than two months after the 9/11 attacks in 2001, was also upset because he did not believe he would be deployed to Afghanistan after his extensive Iraq duty, his lawyer said.

A US official told AFP that Bales was believed to have been drinking prior to the incident, a violation of US combat rules.

The New York Times quoted one official who said Bales may have "just snapped" due to a combination of stress and tensions with his wife, although Browne has rejected reports of his client's marital problems.