Farewell … Corporal Dale Birt mourns the loss of his brother Corporal Ashley Birt at his memorial service yesterday. Photo: Michelle Smith

AN AUSTRALIAN soldier attending a memorial for a comrade shot and killed by a rogue Afghan soldier says it is hard to know who to trust after another attack from a supposed ally overnight.

A memorial service was held yesterday morning at Gallipoli Barracks, Brisbane, for Corporal Ashley Birt, 22, who was killed in Afghanistan on October 29 when an Afghan soldier opened fire on Australian allies.

Captain Bryce Duffy, 26, and Lance Corporal Luke Gavin, 29, were also killed in the attack.

One soldier, who did not want to be named, said he was still digesting the news of the attack.

''It's hard to take. Who do you trust?'' he said. ''But we believe in the mission. We are serving the country.''

Corporal Birt was honoured by his friend and colleague Lance Corporal Matthew Evans, who delivered the eulogy.

''He was always known as the life of the party and his life was a party. He lived it to the fullest,'' Lance Corporal Evans said.

''What Ash has done in his whole life is etched into eternity.

''We all love him.''

Corporal Birt's brother Corporal Dale Birt, read the soldier's prayer to the congregation.