The explosion comes two days after at least 56 people were killed in attacks elsewhere in the country, including women and newborn babies, dealing a setback to peace plans in the war-ravaged nation.

"A car bomb explosion took place near a military court in Gardez city, which is a populated area. Dozens of civilians are feared to be dead and wounded," said Tariq Arian, an interior ministry spokesman.

Taliban spokesman Zabihullah Mujahid in a statement said the rebel group was responsible for the attack.

Emal Khan Momand, a military spokesman in Paktia province where Gardez is located, said the attack was carried out by a truck packed with explosives. Five people were killed and 14 were wounded, he said.

Arian blamed the militant Haqqani network, which has ties to Taliban rebels and the Pakistan-based Lashkar-e-Taiba militant group. These groups rarely publicly claim responsibility for attacks.

The blast comes after gunmen attacked a maternity hospital in Kabul, killing 24 people, including new mothers and newborn babies, on Tuesday. A suicide blast claimed by the Islamic State at a funeral in eastern Nangahar on the same day killed 32.

President Ashraf Ghani condemned the attacks and said he had ordered the military to switch to offensive mode rather than the defensive stance it had adopted as the United States withdraws troops and tries to broker talks with the Taliban.

The Taliban denied any involvement in those attacks, but the government accused the group of fostering an environment in which terrorism thrives or of working with other militant groups who could have been involved, straining efforts by the United States to bring the insurgents and the Afghan government together.