Another two guards were wounded in the attack in western Farah province on Monday, provincial police chief Sayed Agha Saqeb said on Tuesday.
The ambush on the Turkish Kolin company vehicle was on a stretch of road that sees regular attacks, with three Afghans working for foreign groups killed in the area last Thursday.
An official at the Turkish embassy in Kabul speaking to AFP said: "It was a terrorist attack as far as we understand.
"They (Afghan authorities) told us that they used RPGs (rocket propelled grenades) and light weapons."
The Turk who died was a truck driver aged around 48. He was the third Turk to be killed in attacks in Afghanistan this year. His body was due to be repatriated in two days.
The police chief said a hunt had been carried out for the attackers in nearby mountains to where they were believed to have fled.
There are several Turkish companies helping to rebuild Afghanistan's war-ravaged infrastructure, and they as well as other foreign firms have been the target of several attacks by fighters linked to the Taliban.
The Turkish groups came to Afghanistan in 2002, months after the Taliban movement was removed from power by a coalition led by the United States.
Kolin is repairing the main highway between Kandahar city in the south and Herat in the west.
Many Afghan and foreign road workers have been killed, some of them beheaded, in Afghanistan since the Taliban fell.
The fighters have claimed responsibility for some of the killings and warned foreign companies, which the government relies on for reconstruction, to leave Afghanistan and Afghans not to work for them.
Two Afghans working for a Turkish construction company were killed last Thursday when a bomb exploded under their vehicle near the site of Monday's attack.
The same day, an Afghan deminer contracted to the UN demining agency was killed in a bomb blast in the vicinity.
And seven workers at a multinational force-run air base in Kandahar city were killed when a bomb placed in their bus exploded. Three bystanders were also killed.