The latest tragedy, which occurred Wednesday, involves a reservist belonging to The Princess of Wales' Own Regiment, one of the country's oldest military units, based in Kingston, Ont.
Several defence sources identify the victim as Cpl. Camilo Sanhueza-Martinez, 28, a veteran of the Afghan war.
National Defence confirmed the identity, but declined comment on the circumstances saying that Kingston Police were investigating after the soldier was found at home.
"The sudden loss of any soldier is devastating to the military community and our condolences go out to his family and friends," said a defence department statement. "The loss of any of our soldiers is tragic and heartbreaking. The regimental family, the entire army family and community are mourning the loss of Cpl. Sanhueza-Martinez."
He joined the army in January 2005 and served in Afghanistan between May 2010 and January 2011.
Over the last week, there have at least two other cases of apparent suicide involving serving members of the Forces, and that follows on a string of deaths last fall, including a spate of four in one week.
One particularly stark case from December was made public earlier this week when the husband of a former Canadian soldier who died in a Christmas Day car crash in southern Alberta told CTV that his wife's death was a suicide.
Tom MacEachern said his 51-year-old wife, Leona, a retired corporal, was being treated for post-traumatic stress disorder, and intentionally drove her car into an oncoming tractor-trailer on the Trans-Canada Highway near Calgary.
MacEachern says his wife had been locked in a long battle with Veterans Affairs over medical benefits for dental work she received while stationed in Germany during the first Gulf war.
The latest case involving the reservist from Toronto alarms veterans advocates.
While National Defence is able to effectively track regular, full-time members, it has struggled to deliver services to reservists, who serve part-time.
"One can only wonder just what level of mental health support DND is providing an individual at the reservist level or how many more reservists have taken their lives," said Mike Blais, president of Canadian Veteran Advocacy.
"We can not underestimate this problem, thousands of reservists were called upon to serve in Afghanistan. Those who have sustained mental wounds are in our communities. They need our help. They need the help of our military and government."
The alarming number of suspected suicides prompted NDP leader Tom Mulcair to make a direct plea to Prime Minister Stephen Harper on Friday to take "urgent action."
Mulcair sent a letter to Harper calling on him to "commit to taking urgent action" to properly address the mental health needs of those who serve in the military.
"I urge you to make addressing this issue a personal priority for you as prime minister," the letter states.
"I am asking you on behalf of your government to honestly acknowledge the crisis, accept responsibility for the fact the status quo isn't working."
The issue of mental health needs in the military was brought before two separate House of Commons committees last month.
Former soldiers and veterans advocates said little attention is paid to helping physically wounded soldiers and those suffering from Post Traumatic Stress Disorder make the transition to civilian life.
And they said the perceived financial uncertainty created by the Harper government's overhaul of veterans benefits is driving some soldiers to the brink.
The government's New Veterans Charter largely converted the old pension-for-life system to a series of lump-sum awards and finite allowances — something the soldiers claim is far less generous.
Mulcair's letter points out that there have been more than 50 boards of inquiry on military suicides, some of which date back five years and some of which haven't been released.
"In too many cases, grieving families are left without answers or closure," Mulcair writes.
"Canadians are left with grave concerns about whether the system put in place to help our armed forces is broken, or if we are learning from these tragedies in order to prevent future ones."
Jason MacDonald, a spokesman for Harper, said in an email that Canada's military and Veterans Affairs take suicides and stress among current and former soldiers seriously and are making every effort to provide support.
"It's irresponsible for politicians to assert that these services are not available," MacDonald said.
The Harper government has said it the past that it has invested millions bolstering mental health services for the military.
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