Taliban militants claimed responsibility for the attack.

As details emerged about the suicide blast, the governor of Ghazni province said Afghan and NATO forces killed about 30 Taliban fighters and arrested 12 others in Qara Bagh district on Saturday night.

The suicide bomber's apparent target was a convoy of US-led coalition soldiers passing through the market in the city of Gardez in Paktia province, about 100 km (60 miles) south of the capital Kabul.

A spokesman for the US-led coalition said some of its soldiers were wounded in the attack but had no more details. The International Security Assistance Force, which leads thousands of foreign troops in Afghanistan, had initially said its troops were involved but later said the report was wrong.

Taliban insurgents have stepped up attacks after a traditional winter lull in fighting, particularly after the death of the insurgents' top operational commander, Mullah Dadullah, in a raid last weekend. His death was considered the biggest blow to the Taliban since they were driven from power in 2001.