Niamat Allah Shahrani, one of four vice-presidents in the interim government of President Hamid Karzai, was in a convoy with other officials in the northern province of Kunduz when it was attacked, said provincial governor Muhammad Umar Khan.
Karzai, favourite to win a 9 October presidential election, survived an assassination attempt last Friday.
Remnants of the Taliban and armed allies, including al-Qaida, have been blamed for a wave of violence concentrated in the south and east of the country in which about 1000 people have been killed in the last year.
They have vowed to disrupt preparations for the presidential election.
US soldiers killed
Karzai escaped a rocket attack on
his helicopter on Friday
Two soldiers from the US-led coalition hunting al-Qaida and Taliban fighters were killed and two were wounded in a gun battle in the southeastern province of Paktika, a traditional heartland for armed fighters, the US military said.
Six Afghan soldiers had to be evacuated from the scene of the battle, although the US military which leads a 17,000-strong multinational force in Afghanistan did not give details of their wounds.
Other clashes erupted on Monday between US-led forces and suspected fighters in the central province of Uruzgan and the southern province of Zabul.
About 60 US soldiers have been killed in action in Afghanistan since the fall of the Taliban in late 2001.
The nationalities of the two fatalities on Monday were not immediately clear. Over the weekend, suspected Taliban fighters beheaded three Afghan soldiers in Zabul, a local official said on Monday.
Zabul security chief Jailani Khan said the soldiers, who were not in uniform, were travelling in a taxi from Naubahar district to the provincial capital of Qalat when they were stopped by a group of men which included two Pakistanis and an Arab.
"We have already announced that anyone in the government or aiding the infidels will be killed"
Muslim Army of the Taliban
The three passengers were beheaded in an attack claimed by a breakaway Taliban faction.
"We have already announced that anyone in the government or aiding the infidels will be killed," said Sabir Mumin, a commander of the Taliban Jamiat Jaish-e-Muslimin (Muslim Army of the Taliban) faction.
The group announced in August it had broken away from the main Taliban movement, which ruled Afghanistan from 1996 to 2001 before being ousted in a US-led war after it failed to
hand over al-Qaida leader Usama bin Ladin.