While the official anniversary is not until Sunday, a Last Post ceremony was held at the Australian War Memorial on Saturday.

The story of Corporal Geoffrey Hewitt, who was killed in action on June 25, 1941, was highlighted at the ceremony.

Cpl Hewitt and his comrades defended Tobruk for eight months during the Second World War.

The 27-year-old defended his men while they were under attack, using a machine gun to provide cover so his comrades could get away.

He died from a piece of shrapnel and is buried at Tobruk, with his gravestone reading: "He gave his life that truth, honour and justice might prevail."

About 14,000 Australian soldiers worked alongside British and Indian troops to defend the Libyan town and harbour, which was surrounded by German and Italian forces.

They were dubbed as the Rats of Tobruk by enemy forces but the term was embraced and stuck as a nickname.

Cpl Hewitt was one of more than 830 Australians killed during the siege, which ended in December 1941.

Another 2170 were injured and 940 taken as prisoners.

Veterans' Affairs Minister Darren Chester thanked the soldiers for their efforts during the crucial battle.

"As a nation, we remember and thank the Rats of Tobruk for their service and sacrifice," he said.

"Lest we forget."

Australian Associated Press