Commander Ishak Zai Mama, chief of police for southern Ghorak district, and four of his bodyguards were assassinated late last night as they travelled on a road 56 miles northwest of Kandahar, the former spiritual home of the Taliban.
Police spokesman Muhammad Salim Ehsas said the fighters arrived in four pickup trucks and sprayed their vehicle with bullets before fleeing.
Police have launched a manhunt for the gunmen, Ehsas said, adding he believed remnants of the ousted Taliban regime were responsible for the killings.
Salim Khan, a provincial intelligence official, said the clash lasted for more than half an hour but it is not known if the attackers had suffered any casualties.
Kandahar is the former power base of the Taliban, who were driven from power in a US-led invasion in late 2001.
A commander of pro-government forces in the province was attacked by gunmen on Saturday in identical circumstances while returning to his home in nearby Panjwayi district. The officer and his driver were injured in the attack.
Taliban fighters have been blamed for a rash of attacks in recent months, many of them in the south of the country, raising fears in the US-backed administration that the former regime is regrouping.
About 100 Afghan government troops and civilians have been killed or wounded in bomb blasts and rocket strikes across southern Afghanistan since the beginning of the year.
The government and US-led forces have tended to play down the worry of a resurgent Taliban challenging the government but say they are nevertheless capable of launching raids and bomb attacks.
And Afghan officials say Taliban fighters and their al-Qaida allies are plotting their Afghan raids from the safety of neighbouring Pakistan.
Pakistan, which backed the Taliban for years until the September 11 attacks on the United States, says it does all it can to stop fighters crossing back and forth to Afghanistan.
Meanwhile, in another example of the lawlessness that is ravaging the country, two people were killed yesterday in a battle between rival clans of a tribe on the outskirts of Kandahar.
The two clans of the Popalzi tribe exchanged fire with automatic weapons six kilometres northwest of the city. Police claimed today to have restored order at the scene of the fighting.