A Taliban truck bomber killed up to six people in a province south of Kabul Thursday in the first major attack since the terrorist group confirmed the death of their leader Mullah Omar.

A Taliban truck bomber killed six people in a province south of Kabul Thursday, officials said, in the first major attack since the terrorist group confirmed the death of their leader Mullah Omar.

The Taliban claimed responsibility for the attack in Pul-i-Alam, the capital of Logar province in insurgency-prone eastern Afghanistan.

"A water truck filled with explosives was detonated when it was stopped at the gate of the Quick Reaction Force (police) compound," said deputy provincial police chief Mohammad Qari Wara.

"It was a powerful explosion... which killed three members of the Quick Reaction Force and three civilians."

Baheer, an official from the provincial governor's office, confirmed the death toll, adding that eight people including a child were wounded.

Civilian casualties in Afghanistan hit a record high in the first half of 2015, a UN report said Wednesday, as Afghan forces struggle to contain the expanding conflict six months after the NATO combat mission ended.

The report said 1,592 civilians were killed, a six percent fall over last year, while the number of injured jumped four percent to 3,329. The casualties have reached their highest level since the UN began issuing its authoritative reports in 2009.