German soldiers are part of the Kabul peacekeeping force

"An international presence in Afghanistan must be ensured," German Defence minister Peter Struck said.

Saturday's attack in the capital, Kabul, occurred when a taxi filled with explosives drove into a bus carrying German troops.

The Afghan authorities have blamed the Taleban or al-Qaeda.

The apparent suicide attack was the deadliest assault on international peacekeepers since they began their mission in Kabul more than a year ago.

It occurred near a base used by troops from Germany and the Netherlands, who lead the International Security Assistance Force (Isaf).

The targeted bus was taking German soldiers to the airport, to be flown home after a six-month tour of duty.

The other 29 peacekeepers on board were injured, as were several Afghan civilians who were near the scene.

Condolences

Mr Struck said the attack had "a new and horrible dimension" but said it would not lead to Germany changing its stance in Afghanistan.

PEACEKEEPING FORCE Isaf has UN mandate to help Afghan Transitional Authority maintain security Aims to develop reliable security structures, identify reconstruction needs and train Afghan security forces Comprises 4,600 troops from 29 nations, currently led by Germany and the Netherlands Area of responsibility limited to Kabul and vicinity Commander is Lt General Norbert van Heyst of the German Army

He said German troops would neither be pulled out nor ordered to cut themselves off from the Afghan population.

"Confidence cannot be created if we hide in armoured vehicles," Mr Struck said.

"My Afghan colleague told me in a telephone call there are indications that al-Qaeda is behind it," he added.

"This nevertheless still has to be investigated further."

President Hamid Karzai offered his condolences and said the peacekeepers had given their lives for the Afghan people.

German Chancellor Gerhard Schroeder denounced the attack as the "cowardly and devious" work of terrorists.

Belgium, France, Pakistan and the United States also condemned the attack.

More attacks

About 5,000 international peacekeepers have been deployed to patrol the streets of Kabul.

A helicopter landed to provide medical assistance

Anti-government forces have been issuing pamphlets calling on Afghans to rid their country of the peacekeepers.

Militants have been stepping up attacks in recent weeks, particularly in the south and east of Afghanistan.

About 40 Taleban fighters were killed recently in the south in a battle with government forces.

Saturday's explosion was the second violent incident involving German peacekeepers in Kabul in recent weeks.

On 29 May, a German soldier was killed and another wounded when their vehicle hit a landmine near Kabul.