The suicide rate among active duty service members was 24.8 suicides per 100,000 service members last year, the Pentagon's Annual Suicide Report (ASR) found, up from 21.9 in 2017 and 21.5 in 2016. In 2013, there were 18.5 suicides per 100,000 service members.
The report also found that 541 service members were confirmed or believed to have died by suicide last year, up from 511 in 2017. Of those deaths, 325 took place among active-duty service members, while 81 were among members of the Reserves and 135 were among the National Guard.
"There is still much more work to be done," the department said while acknowledging it has "made strides in establishing an infrastructure for preventing military suicide by aligning our strategy with the public health approach."
The ASR found that those service members who died by suicide were primarily enlisted men under 30 who used a gun to kill themselves, the department said.
The National Guard had the highest suicide rate, with 30.6 deaths per 100,000 members, the report says, while the Reserve component saw 22.9 deaths by suicide per 100,000 Reservists, according to the data.
The Army, Navy and Marine Corps all saw the rate of suicides go up as well as the overall numbers, with only the Air Force showing a decrease. Army suicides went from 114 to 139, while the Marines went from 43 to 58 and the Navy went from 65 to 68. The Air Force dipped from 63 to 60.
The report estimates that there were also 186 reported suicides among military spouses and dependents in 2017, the most recent year for which data is available. This was also the first time the Pentagon reported on military family deaths by suicide.
Despite the worrying trends, the report says that after adjusting for age and sex, military suicide rates -- except those among National Guard members -- were roughly equivalent to rates in the larger U.S. population.
"Based on findings from the ASR, the department will use a multi-faceted public health approach to target areas of greatest concern, specifically young and enlisted members, as well as National Guard members, and continue to support our military families," the report states.
In a joint statement, Acting Army Secretary Ryan D. McCarthy and Army Chief of Staff Gen. James C. McConville called the ASR's findings "disheartening and disappointing."
"Suicide is devastating to families and units, and tears at the fabric of our institution," they said. "Leadership at every level must build cohesive 'teams of teams' supporting our brothers and sisters to our left and right. The more we know about each other, the better equipped we are to recognize a call for help."
"We will continue to take a hard look at the challenges we face with suicide to ensure the proper resources are in place to protect those at risk," the officers added.
Defense Secretary Mark Esper addressed suicide among service members on a visit to Naval Station Norfolk in Virginia earlier this week after three Navy sailors assigned to the Norfolk-based USS George H.W. Bush aircraft carrier committed suicide in separate incidents last week.
"You mourn for the families and for their shipmates," he said, the Daily Press reported. "I wish I could tell you we have an answer to prevent future further suicides in the armed services. We don't."
"We believe engaged leadership, focused training and education will promote a supportive environment, prevent high-risk behaviors and increase Army readiness," McCarthy and McConville also said.
"The Army is about people and our team, and we are focused on strengthening resilience, increasing help-seeking behaviors and reducing suicides. To assist our command teams and first-line leaders, we have developed leader visibility tools and enhanced resilience and suicide-prevention training and education," they noted.
"Seeking help is not a sign of weakness; it is a sign of strength," the leaders stressed. " All of us are responsible for the care and safekeeping of our teammates and their families, and for being there for one another and encouraging those in need to get help."
Fox News' Jennifer Griffin contributed to this report.