"I heard of this underhanded attack with great shock," Merkel said in a statement released in Berlin. "This perfidious murder fills all of us with disgust."

She said the bombing was aimed at preventing the process of reconstruction in Afghanistan from becoming a success," but added that the international community was resolved to continue helping Afghans create a better future for themselves.

Three German soldiers were killed and three wounded while six Afghan civilians were killed and 14 others wounded when a suicide attacker detonated his explosive-laden vest in northern Afghanistan, officials said.

Provincial governor Mohammad Omar told German news agency dpa that three German soldiers were killed and two soldiers and an interpreter were wounded when the bomber struck in Chaiferoshi market in Kunduz on Saturday morning. Six Afghan shopkeepers and civilian passers-by were killed and another 14 were wounded, Omar said.

"We received intelligence information a couple of days ago that four would-be suicide bombers entered the city and would use motorcycles to carry out their attacks," Omar said, adding that the police started searching motorbikes on Thursday.

He said that the security forces would intensify their search to track down the remaining bombers.

General Noor Mohammad Omarkhail, provincial security chief of the Kunduz police, described the condition of seven of the wounded Afghans as critical.

Taliban claims responsibility

A spokesperson for the NATO-led International Security Assistance Force (ISAF) in Kabul confirmed the incident in a statement, but said that three ISAF soldiers and five Afghans were killed and 10, including two ISAF soldiers, were wounded.

"This senseless act of violence shows the barbarity of extremists and criminals targeting civilians and ISAF troops who are working to rebuild Afghanistan," Lieutenant Colonel Angela Billings, an ISAF spokeswoman was quoted in the statement as saying.

Taliban militants took responsibility for the attack and said 11 German soldiers were killed in the suicide blast that destroyed the windows of the shops as far as one kilometer (0.6 miles).

"Today at 11:00 a.m. a mujahedeen hero, Jawad, who is a resident of Kunduz province, attacked the German soldiers who were patrolling in the area," Zabeeullah Mujahed, a Taliban spokesman said in a statement posted at their Web site.

At the German Defense Ministry in Berlin, officials declined to confirm any death toll, speaking only of "several" soldiers being killed, which was taken as a hint that the German wounded were in critical condition.

Debate expected in parliament

Voicing shock at the attack, German Defense Minister Franz Josef Jung broke off a private weekend trip and flew back to Berlin to respond to the crisis.

The attack was expected to lead to renewed debate in Germany about whether German soldiers should be posted to Afghanistan.

Germany's Green party, which has supported the Afghan peace mission, appeared to be foreshadowing that debate Saturday, calling for a massive rise in spending on training the Afghan military.

The Green parliamentary co-leaders said the attack was "intended to stop the establishment of democratic structures."

German television reported that the soldiers got out of their patrol vehicle to do some shopping.

21 German dead

It was the biggest suicide attack against German troops in Afghanistan since June 2003 when four German soldiers were killed and 29 wounded.

Apart from Saturday's incident, 18 German soldiers have been killed in Afghanistan since the ouster of the Taliban regime in late 2001. Ten of them were killed by hostile acts while eight died in non-combat incidents.

There are around 3,000 German troops under the banner of the NATO- led International Security Assistance Force (ISAF) in the country, the bulk of them stationed in the northern provinces.

Northern provinces of the country are relatively calm. However, on April 16, a suicide attack targeted a police training center in Kunduz city, killing nine policemen and wounding 25 others.