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A New Zealand-born Australian soldier has been killed in a roadside bombing in Afghanistan, defence chief Angus Houston said this morning.

Air Chief Marshal Houston said the dead soldier was Signaller Sean McCarthy, 25, from the Perth-based Special Air Service Regiment (SASR).

Signaller McCarthy died as a result of an improvised explosive device (IED) which also injured two other Australian soldiers and a soldier from another country at 3pm yesterday, he said.

Air Chief Marshal Houston said the three soldiers and the other coalition national were evacuated to coalition medical facilities immediately after the incident.

"Despite receiving the best possible medical attention, Signaller McCarthy succumbed to his wounds," he said.

"The injuries to the remaining two soldiers do not appear to be life-threatening. However they and the coalition national who was seriously wounded continue to be closely monitored."

Air Chief Marshal Houston said that because the injured soldiers were special forces their details would not be made public.

He said Signaller McCarthy had joined the Australian Defence Force in 2001 and joined the SAS last year.

Signaller McCarthy had served in East Timor earlier this year and was on his second tour of Afghanistan.

"On his previous tour in Afghanistan, he was recognised by the special operations commander for his courage and mission focus, including a specific commendation for maintaining his presence of mind and excellent soldier's skills while in contact with the enemy," Air Chief Marshal Houston said.

"Signaller McCarthy was an experienced, highly skilled and professional soldier.

"He was very well respected by his comrades and will be sorely missed by his many friends."

Air Chief Marshal Houston said investigations were continuing into exactly what type of improvised explosive devise was used in the attack.

"In experience most of them are pressure plate devices but in more recent times we are starting to see radio control devices and command initiated devices," he said.

"Until we actually do a full investigation I can't inform you as to exactly what type of device it was and how it was triggered."

Air Chief Marshal Houston said he could not reveal the location of the attack.

"I would love to tell you where it is but the patrol is still out there, they're doing important work and I would not be prepared to endanger the lives of our people for operational security reasons."

Air Chief Marshal Houston said the incident would be a "trigger for more and more active operations against the people who produce these dreadful weapons."

"This will harden our resolve to keep these Taliban leaders, these Taliban bomb makers under pressure, we will continue to go after them and we will continue to disrupt their activities."

Signaller McCarthy was not married and his next of kin, who are travelling in Europe, have been informed of his death.

He is the second Australian soldier killed in Afghanistan this year. On April 27, Lance Corporal Jason Marks, 27, from 4RAR commando unit in Sydney was killed in battle with Taliban fighters in Oruzgan province.

Three other soldiers were killed in separate incidents last year. They were Private Luke Worsley from 4RAR, SAS Sergeant Matthew Locke, and Trooper David Pearce.

Sergeant Andrew Russell, 33, was killed in southern Afghanistan in 2002.