Key Points:

Australia has vowed to step up search-and-destroy operations against the Taleban after a New Zealand-born special forces trooper was killed in Afghanistan.

Sean McCarthy, 25, a decorated SAS signaller whose courage had been recognised in an earlier tour of duty in Afghanistan, was killed by a bomb on Tuesday afternoon during a patrol that continued in Taleban territory yesterday.

The bomb, known as an improvised explosive device, also wounded two other SAS troopers and a soldier from a Coalition ally. Their wounds were described as serious but not life-threatening.

Signaller McCarthy is the sixth Australian soldier to be killed in Afghanistan since 2002. A further 40 have been wounded.

"This will harden our resolve to keep these Taleban leaders, these Taleban bomb-makers, under pressure," said defence chief Air Chief Marshal Angus Houston.

Signaller McCarthy, who was born in Auckland but grew up on the Gold Coast, died after the bomb exploded near his vehicle during a patrol in an area suspected of harbouring Taleban fighters.

Air Chief Marshal Houston said the four soldiers were flown by helicopter to a military hospital, but Signaller McCarthy had succumbed to his wounds.

A keen rugby fan who had played in the 2nd XV at the Gold Coast's Trinity Lutheran College, Signaller Houston enlisted in the Army in July 2001, joined the Signals Regiment in 2003 and transferred to the Perth-based SAS Regiment in January last year.

He was deployed with the Special Operations Group in Afghanistan in 2007, worked in East Timor this year, and less than a month ago returned to Afghanistan.

"On his previous tour of 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.

He said Signaller McCarthy was a highly skilled and professional soldier who was well respected by his comrades and would be sorely missed by his many friends.

Signaller McCarthy's parents have been on holiday in Europe.

"I cannot ease their grief, but I want them to know they are in our thoughts and prayers," Air Chief Marshal Houston said.

Prime Minister Kevin Rudd, who warned the nation to expect more deaths when commando Lance Corporal Jason Marks became the fifth Australian to be killed in Afghanistan, said Signaller McCarthy had been a fine soldier in the best traditions of the Australian Defence Force.

The work of the special forces task group, a force of about 300 SAS troopers and commandos, is especially dangerous, hunting down and pushing Taleban from an extending perimeter around Australia's base in Oruzgan province.

Reconstruction engineers, protected by infantry and armour, work within the perimeter.

Air Chief Marshal Houston said improvised explosive devices were the biggest threat to Australian troops, accounting for 70 per cent of recent Coalition casualties.

He said special forces, who in the past three weeks alone had destroyed a bomb factory, captured two Taleban leaders and uncovered a large cache of weapons, would continue aggressive patrolling.

New Zealand Defence Minister Phil Goff said the death highlighted "risks to the lives of our soldiers, in defence of our country and the values that we uphold".

"The tragedy of a young man aged 25 losing his life while serving with international forces in Afghanistan is a reminder of the costs that our contribution to seeking to secure peace and stability in that country involves.

"On behalf of the New Zealand Defence Force in particular, we express our sympathies and pay tribute to the life of Sean McCarthy, who died in the service of our countries."

SAS Signaller Sean McCarthy
* Born January 5, 1983, in Auckland.
* Enlisted in the Australian Defence Force on July 10, 2001.
* Posted to 7 Signals Regiment on July 14, 2003.
* Posted to Special Air Service Regiment (SASR) on January 15, 2007, and was an active member up to his death.

Operational service includes:
* Special Operations Task Group (SOTG V) Afghanistan, 2007.
* Operation Astute in East Timor, 2008.
* Redeployed to Afghanistan, 2008.

Awards and commendations:
* SOCAUST commendation.
* Australian Defence Medal for service.
* International Coalition Against Terrorism Clasp.
* Afghanistan Campaign Medal.
* Nato Medal.
* Return from Active Service Badge.