Attack in Afghanistan

German Interior Minister Wolfgang Schäuble on Wednesday confirmed that the men were all German police officers.

A fourth man injured in the bombing is also a German police officer. The men were on their way to a shooting range at Bagrami east of Kabul when the bomb was detonated.

Schäuble said that the police officers were all attached to the embassy and not part of the European Union police mission EUPOL that trains Afghan police officers.

The officers had been traveling in a "specially protected vehicle," Schäuble said, but this had still not been able to protect them.

The German Federal Criminal Police (BKA), to which the officers were attached, would send forensic experts to Kabul to probe the incident, he said.

Schäuble said Germany would continue its efforts to train Afghanistan's security forces in cooperation with its EU partners.

"Afghanistan needs our continued support," he said.

German Foreign Minister Frank-Walter Steinmeier meanwhile said he was "appalled" by the deaths and called for those behind the blast to be found and punished.

Alishan Paktiwal, the top investigator for the Kabul police, told Deutsche Presse-Agentur dpa that a roadside bomb detonated on the outskirts of the Afghan capital as two vehicles were passing.

One of the vehicles was destroyed, he said, adding that it carried a German flag. Eyewitnesses said that both vehicles were white off-road vehicles of a type used by the German embassy.

Taliban claim responsibility

The Taliban said on its Web site that it had destroyed a foreign military vehicle in a bombing in Bagrami. It claimed nine soldiers were killed, but its casualty figures are often exaggerated.

In May, three German soldiers were killed along with five Afghan civilians in a suicide bombing in the northern city of Kunduz.

Amid the rising casualties, public support has fallen in Germany for the country's missions in Afghanistan.

German politicians back mission

Following the bombing, political leaders from the two main parties backed Germany's continued involvement in the country.

The German parliament is to debate the renewal later this year of three separate mandates relating to the deployment of German military and police to Afghanistan.

There are some 3,000 German troops engaged in a reconstruction mission in northern Afghanistan within the NATO-led International Security Assistance Force (ISAF).

Six German reconnaissance aircraft, with support personnel, were sent to Afghanistan in April to assist ISAF combat operations mainly in the south of the country.

There is also a mandate for German troops -- particularly special forces -- to assist the US-led counter-terrorism Operation Enduring Freedom.