Two Australian soldiers have been killed in separate incidents in Afghanistan.
Their deaths bring to 26 the number of diggers to die in Afghanistan since operations began in 2001.
The incidents on Monday coincided with the arrival home of the body of Sergeant Brett Wood who was killed in Afghanistan more than a week ago in a bomb blast which also injured two other soldiers.
Defence force chief Angus Houston said it was "a very bad day" for the Australian Defence Force.
"It was with immense sorrow that I am here this morning to announce the death of two Australian soldiers in Afghanistan in two separate incidents overnight," he told reporters in Canberra on Tuesday.
The first soldier was killed when he was shot by an Afghan National Army soldier while both were on guard duty on Monday evening.
The second soldier, an army lieutenant, died when a Chinook helicopter crashed a few hours after the first incident.
The other five Australian soldiers in the helicopter were evacuated from the crash site and taken to hospital in Kandahar in a satisfactory condition.
The first incident took place at Patrol Base Marshal in the Chora Valley.
"Despite receiving substantial medical treatment at the base and being airlifted very quickly to a nearby medical facility at Tarin Kowt in well under an hour the Australian soldier died from his wounds," Air Chief Marshal Houston said.
The Afghan soldier who fired his weapon fled the scene.
Another Afghan army soldier fired upon his colleague as he was fleeing.
Air Chief Marshal Houston said it was yet to be determined whether the fatal shooting was accidental or deliberate.
"I am unable to say at this time," he said.
The Afghan soldier has yet to be apprehended.
Air Chief Marshal Houston said the circumstances of the 25-year-old soldier's death were disturbing, given that Australian personnel were training and mentoring elements of the Afghan National Army.
"I can't speak today about the motivation of this Afghan National Army soldier or any associations he may have or the amount of planning that did or didn't go into the attack."
The entire event is now under investigation by defence.
"We're obviously going to take a very close look how this occurred, why this occurred and what if anything could have been done to prevent it," Air Chief Marshal Houston said.
The name of the lance corporal from Queensland could not be released at this stage, Air Chief Marshal Houston said.
He had served in the Australian Army for seven years with operational experience in East Timor and started his rotation in Afghanistan last year, he said.
"I am told he was a loyal, reliable and very trusted member of his unit," Air Chief Marshal Houston said, adding the digger was promoted in 2010 and displayed "great leadership potential".
"Though he was quiet and reserved he enjoyed a joke with his mates and was always the first among them to volunteer when work was required."
The soldier's comrades in the Australian mentoring taskforce were now coping with the death of a mate and also "with this perpetrator".
"They will be experiencing myriad emotions, grief and anger amongst them," Air Chief Marshal Houston said.
"I also know they will want to reaffirm their commitment to the Afghan partners with whom they enjoy a productive, trustworthy and close relationship.
"They will not want this terrible incident to damage the outstanding progress made by many rotations of mentors and their Afghan partners."
The defence force remain committed to its mentoring role, Air Chief Marshal Houston said.
The commander of the Afghan National Army brigade working with Australian mentors had expressed his shock and outrage at the attack, Air Chief Marshal Houston said.
"He and his soldiers are actively seeking to apprehend the suspect."
The defence force chief said the incident would "quite rightly" raise some very serious questions about what security measures were in place.
In the second incident, an Australian Chinook helicopter crashed 90km east of Tarin Kowt while on a resupply mission.
A nearby US Chinook provided assistance to the six Australians on board the crashed chopper.
Despite immediate medical assistance the 27-year-old Army lieutenant from Victoria could not be saved, Air Chief Marshal Houston said.
The other five soldiers were evacuated to a medical facility at Kandahar where they were in a satisfactory condition.
The helicopter could not be recovered and was destroyed "in place".
"The family of this soldier were notified about his death this morning," Air Chief Marshal Houston said, adding the officer's name could not be released at this stage.
The lieutenant, who was a trained pilot, had provided "sterling service" in Afghanistan since being deployed a short time ago, he said.
He had previously had served in East Timor and had been part of Operation Flood Assistance in Queensland earlier in 2011.
Air Chief Marshal Houston said the lieutenant's comrades had described him as a "keen, motivated and driven" young officer, committed to serving his nation.
"To this officer's large and close-knit family I offer my deepest sympathy and assure them we will provide whatever assistance required."
Defence Minister Stephen Smith said the tragic news would be a devastating blow to the soldiers' families and the nation.
"This sad news will reverberate throughout Australia in the course of today," he told reporters.
Rest In Peace, my brothers.
Their deaths bring to 26 the number of diggers to die in Afghanistan since operations began in 2001.
The incidents on Monday coincided with the arrival home of the body of Sergeant Brett Wood who was killed in Afghanistan more than a week ago in a bomb blast which also injured two other soldiers.
Defence force chief Angus Houston said it was "a very bad day" for the Australian Defence Force.
"It was with immense sorrow that I am here this morning to announce the death of two Australian soldiers in Afghanistan in two separate incidents overnight," he told reporters in Canberra on Tuesday.
The first soldier was killed when he was shot by an Afghan National Army soldier while both were on guard duty on Monday evening.
The second soldier, an army lieutenant, died when a Chinook helicopter crashed a few hours after the first incident.
The other five Australian soldiers in the helicopter were evacuated from the crash site and taken to hospital in Kandahar in a satisfactory condition.
The first incident took place at Patrol Base Marshal in the Chora Valley.
"Despite receiving substantial medical treatment at the base and being airlifted very quickly to a nearby medical facility at Tarin Kowt in well under an hour the Australian soldier died from his wounds," Air Chief Marshal Houston said.
The Afghan soldier who fired his weapon fled the scene.
Another Afghan army soldier fired upon his colleague as he was fleeing.
Air Chief Marshal Houston said it was yet to be determined whether the fatal shooting was accidental or deliberate.
"I am unable to say at this time," he said.
The Afghan soldier has yet to be apprehended.
Air Chief Marshal Houston said the circumstances of the 25-year-old soldier's death were disturbing, given that Australian personnel were training and mentoring elements of the Afghan National Army.
"I can't speak today about the motivation of this Afghan National Army soldier or any associations he may have or the amount of planning that did or didn't go into the attack."
The entire event is now under investigation by defence.
"We're obviously going to take a very close look how this occurred, why this occurred and what if anything could have been done to prevent it," Air Chief Marshal Houston said.
The name of the lance corporal from Queensland could not be released at this stage, Air Chief Marshal Houston said.
He had served in the Australian Army for seven years with operational experience in East Timor and started his rotation in Afghanistan last year, he said.
"I am told he was a loyal, reliable and very trusted member of his unit," Air Chief Marshal Houston said, adding the digger was promoted in 2010 and displayed "great leadership potential".
"Though he was quiet and reserved he enjoyed a joke with his mates and was always the first among them to volunteer when work was required."
The soldier's comrades in the Australian mentoring taskforce were now coping with the death of a mate and also "with this perpetrator".
"They will be experiencing myriad emotions, grief and anger amongst them," Air Chief Marshal Houston said.
"I also know they will want to reaffirm their commitment to the Afghan partners with whom they enjoy a productive, trustworthy and close relationship.
"They will not want this terrible incident to damage the outstanding progress made by many rotations of mentors and their Afghan partners."
The defence force remain committed to its mentoring role, Air Chief Marshal Houston said.
The commander of the Afghan National Army brigade working with Australian mentors had expressed his shock and outrage at the attack, Air Chief Marshal Houston said.
"He and his soldiers are actively seeking to apprehend the suspect."
The defence force chief said the incident would "quite rightly" raise some very serious questions about what security measures were in place.
In the second incident, an Australian Chinook helicopter crashed 90km east of Tarin Kowt while on a resupply mission.
A nearby US Chinook provided assistance to the six Australians on board the crashed chopper.
Despite immediate medical assistance the 27-year-old Army lieutenant from Victoria could not be saved, Air Chief Marshal Houston said.
The other five soldiers were evacuated to a medical facility at Kandahar where they were in a satisfactory condition.
The helicopter could not be recovered and was destroyed "in place".
"The family of this soldier were notified about his death this morning," Air Chief Marshal Houston said, adding the officer's name could not be released at this stage.
The lieutenant, who was a trained pilot, had provided "sterling service" in Afghanistan since being deployed a short time ago, he said.
He had previously had served in East Timor and had been part of Operation Flood Assistance in Queensland earlier in 2011.
Air Chief Marshal Houston said the lieutenant's comrades had described him as a "keen, motivated and driven" young officer, committed to serving his nation.
"To this officer's large and close-knit family I offer my deepest sympathy and assure them we will provide whatever assistance required."
Defence Minister Stephen Smith said the tragic news would be a devastating blow to the soldiers' families and the nation.
"This sad news will reverberate throughout Australia in the course of today," he told reporters.
Rest In Peace, my brothers.
