"The bombing took place in Khairabad area of the Baharak district during daytime when Governor Mohammad Nazir's motorcade was passing by the area," Xinhua quoted the spokesman as saying.
The bodies of the guards killed in the attack were shifted to a hospital in provincial capital of Faizabad, 315 km northeast of national capital Kabul.
Recently, Afghan officials and pro-government figures have been repeatedly targeted by Taliban insurgents. Up to 312 civilians were killed and 131 were wounded in targeted killings across the country in the first half of the year, official sources confirmed.
An army division was dispatched to the province to help strengthen security forces.