WASHINGTON — The number of Army suicides increased again last year, amid the most violent year yet in both the Iraq and Afghanistan wars.

Two defense officials said Thursday that 108 troops committed suicide in 2007, six more than the previous year. The officials spoke on condition of anonymity because the full report on the deaths wasn’t being released until later Thursday.

About a quarter of the deaths occurred in Iraq.

The overall toll was the highest in many years, and it was unclear when, if ever, it was previously that high. Immediately available Army records go back only to 1990 and the figure then was lower — at 102 — for that year as well as 1991.

The 108 confirmed deaths in 2007 among active duty soldiers and National Guard and Reserve troops that had been activated was lower than previously feared. Preliminary figures released in January showed as many as 121 troops might have killed themselves, but a number of the deaths were still being investigated then and have since been attributed to other causes, the officials said.

Suicides have been rising during the five-year-old war in Iraq and nearly seven years of war in Afghanistan.

The 108 deaths last year followed 102 in 2006, 85 in 2005 and 67 in 2004.

More U.S. troops also died overall in hostilities in 2007 than in any of the previous years in Iraq and Afghanistan. Overall violence increased in Afghanistan with a Taliban resurgence and overall deaths increased in Iraq, even as violence there declined in the second half of the year.

Increasing the strain on the force last year was the extension of deployments to 15 months from 12 months, a practice ending this year.

The increases in suicides come despite a host of efforts to improve the mental health of a force stressed by the long and repeated tours of duty.

The efforts include more training and education programs, such as suicide prevention programs and a program last year that taught all troops how to recognize mental health problems in themselves and their buddies. Officials also approved the hiring of more than 300 additional psychiatrists, psychologists and other mental health professionals and have so far hired 180 of them. They also have added more screening to measure the mental health of troops.

Earlier this year, Lt. Gen. Michael Rochelle, the deputy chief of staff for personnel, directed a complete review of the Army’s suicide prevention program, according to the Army’s Web site. He called for a campaign that would make use of the best available science, and would raise awareness of the problem.

“Since the beginning of the global war on terror, the Army has lost over 580 soldiers to suicide, an equivalent of an entire infantry battalion task force,” the Army said in a suicide prevention guide to installations and units that was posted in mid-March on the site.

“This ranks as the fourth leading manner of death for soldiers, exceeded only by hostile fire, accidents and illnesses,” it said. “Even more startling is that during this same period, 10 to 20 times as many soldiers have thought to harm themselves or attempted suicide.”

The numbers kept by the Army only show part of the picture because they don’t include guard and reserve troops who have finished their active duty and returned home to their civilian jobs.

The Department of Veterans Affairs tracks the number of suicides among those who have left the military. It says there have been 144 suicides among the nearly 500,000 service members who left the military from 2002-2005 after fighting in at least one of the wars.

The true incidence of suicide among veterans is not known, according to a recent Congressional Research Service report. Based on numbers from the Centers for Disease Control and Prevention, the VA estimates that 18 veterans a day — or 6,500 a year — take their own lives, but that number includes vets from all wars.