BAGHDAD -- An American soldier serving in Iraq was arrested Monday on suspicion of fatally shooting five fellow soldiers at a U.S. base in Baghdad, the military said.
The shooting took place at about 2 p.m. local time at Camp Liberty near Baghdad International Airport, the military said in a statement. Officials said the shooting was under investigation but they wouldn't answer any further questions about what happened.
At about the same time as the Camp Liberty shooting, another American soldier died in a roadside bomb attack in the southern province of Basra, the military said in a separate statement.
The identities of all the soldiers who were killed are being withheld pending notification of their families, the military said.
Officials also wouldn't name the shooting suspect.
"Anytime we lose one of our own, it affects us all," spokesman Col. John Robinson said in the military's statement about the shootings. "Our hearts go out to the families and friends of all the service members involved in this terrible tragedy."
Several news agencies reported that the killings took place at a counseling center at Camp Liberty, but the military wouldn't confirm that.
A number of recent studies have concluded that a significant portion of soldiers who have served in Iraq suffer from post-traumatic stress disorder and other stress-related mental illnesses.
There have been several incidents since the start of the war in which U.S. soldiers have killed comrades, but Monday's appears to be the deadliest so far.
The last such case was in September, when Sgt. Joseph Bozicevich of Minneapolis, Minn., allegedly shot and killed two soldiers in his unit at a U.S. base south of Baghdad. Bozicevich has yet to be tried.
The last time that five or more soldiers died in a single incident in Iraq was April 10, when a suicide bomber driving a truck packed with explosives slammed into a gate outside an Iraqi national police station in the northern city of Mosul.
Five Americans died in the attack.
Deaths among U.S. soldiers in Iraq are on the rise. Eighteen were killed in Iraq last month, the highest monthly toll since September.
With Monday's attacks, 10 American soldiers have died so far this month.
Overall violence has been increasing here since March.
More than 200 Iraqis died in explosions in Baghdad last month, according to a McClatchy Newspapers count.
The last time McClatchy recorded a higher civilian toll was more than a year ago.
Reporter Corinne Reilly can be reached at email@example.com.