The two Australian soldiers who were killed in a helicopter crash in Afghanistan this week have been named. One of them was engaged to get married.

Defence chief David Hurley told reporters that Private Nathanael Galagher, 23, from Wee Waa in NSW and Lance Corporal Mervyn McDonald, 30, from Carnarvon in Western Australia were the two victims of the fatal crash.

The two soldiers were among five men killed in two separate incidents this week.

Lieutenant General Hurley said Private Galagher joined the army in 2007 and was on his second deployment to Afghanistan. He had left behind his domestic partner, parents and sister.

Lance Corporal McDonald joined the army in 1999. He left in 2004, but re-enlisted in 2005. He was on his sixth deployment to Afghanistan. He had left behind his fiancée, mother, stepfather and three brothers.

Meanwhile, Lieutenant General Hurley said families of three men killed in an insider attack by a member of the Afghan National Army are not yet ready to have their personal details released.

"We all feel this loss deeply," he said.

Sergeant Hek Matullah, the suspected insider who shot three soldiers at a patrol base in the Baluchi Valley this week, is believed to have connections with the Taliban group. However, Lieutenant General Hurley said they are still investigating.

"We are not yet aware of any relationship he has with the Taliban," he said.

The Taliban had earlier claimed responsibility for all insider attacks, but the general said they are still looking into piece of evidence.

"The evidence does not necessarily support [the Taliban's statement]," he said.

"But regardless of these motives, these attacks will be used by the insurgency to undermine our confidence and our relationship with the ANSF."