RFE/RL's Radio Free Afghanistan reports that two of Governor Arsala Jamal's bodyguards were killed in the attack.
Hospital officials in Khost said that four of Jamal's bodyguards and eight civilians also were injured.
The attack occurred close to a base for U.S.-led coalition forces just to the east of the town of Khost.
Jamal, who was returning from a ceremony marking the start of a road project near the border with Pakistan, says he was not hurt. But he said he saw "people in flames in cars" that were ahead of his vehicle in the convoy.
New Taliban Attacks
Meanwhile today, NATO said that Taliban militants wearing Afghan Army uniforms attacked an alliance base in eastern Afghanistan's Nuristan Province.
A statement released by the alliance said that two Afghan soldiers were killed and 11 NATO soldiers wounded in the attack on a forward operating base. The nationalities of the wounded NATO troops were not released.
(with material from agency reports)