Kabul, Afghanistan ? A uniformed man on a motorbike detonated a bomb Wednesday outside an Afghan army training center where soldiers were waiting to take buses home, killing nine people and wounding 28 in a rare suicide attack.

The blast broke 10 days of relative calm after landmark parliamentary elections and underscored the terrorist threat still facing Afghanistan as it slowly moves toward democracy. It also added to fears that insurgents here are copying tactics used in Iraq.

A purported Taliban spokesman claimed responsibility and threatened more suicide attacks on U.S. and Afghan forces. His account of the bombing differed from those of witnesses, however, and his claims could not immediately be verified.

Defense Ministry spokesman Gen. Mohammed Zaher Azimi said authorities had yet to identify the bomber but blamed “international terrorists.” He did not elaborate. President Hamid Karzai condemned the attack in “the strongest terms” as he ordered authorities to investigate.

The attack targeted the U.S.-trained Afghan National Army, which currently numbers about 30,000 and is a key plank of international efforts to rebuild the country.

Gen. Ghulam Saki, commander of the Kabul Military Training Center, said nine army personnel died, as well as the attacker. Three civilian bus workers were among 28 people treated in a military hospital.

This year has seen a surge in violence in Afghanistan, mostly in the volatile south and east where Taliban-led insurgents are strongest. More than 1,300 people, many of them rebels, have died in the past seven months.

Kabul – patrolled by thousands of NATO peacekeepers – is regarded as one of the country’s safest places, despite a flurry of kidnappings of foreigners over the past year. The last major explosion here was in August 2004, when a car bomb tore through the office of a U.S. contractor providing security for Karzai, killing 10 people. The Taliban claimed responsibility.

Witnesses said Wednesday’s attacker wore a uniform and rode a motorbike into the parking lot of the eastern Kabul training center as officers and soldiers waited to take minibuses home around 4 p.m.

NATO peacekeepers with tanks and armored personnel carriers blocked roads to the blast scene. But an Associated Press reporter who gained access saw three blackened, badly damaged minibuses, one lying on its side. Investigators worked under floodlights, while peacekeepers with flashlights searched nearby woods.

Suicide assaults are far less frequent in Afghanistan than by insurgents opposed to U.S.-led forces in Iraq, although senior Afghan officials have spoken in recent months of al-Qaida operatives entering the country to stage attacks.