An Afghan official says at least five civilians were killed when their vehicle hit a roadside bomb in southern Kandahar province.

Samim Khpolwak, the governor's spokesman, says the explosion, which took place in Shah Wali Kot district early on Tuesday, also wounded four people.

No group has claimed responsibility for the attack. Kandahar is regarded by the Taliban as their heartland. It had been largely peaceful for some years until a recent resurgence in insurgent violence.

In neighboring Helmand province, police chief Noor Agha Kemtoz says the Taliban shadow governor, Abdul Manan, was killed by Afghan security forces in Marjah district late on Monday.

However, Taliban spokesman Qari Yusouf Ahmadi denied reports of Manan's death. The Taliban have set up many provincial "shadow" administrations mirroring the government.