The attacks were the latest in an upsurge of Taliban-linked violence that has left nearly 70 people dead over the past week, including more than 40 fighters and five foreigners - three of whom were civilians.
The violence, which includes three botched suicide blasts that killed only the attackers, comes about two weeks after Mullah Omar, the Taliban's fugitive leader, promised a stepped-up spring offensive.
The Turkish engineer was killed on Sunday when attackers stopped the vehicle he was in with three bodyguards in western Farah province, the governor of neighbouring Nimroz province said.
"Armed Taliban in a station wagon stopped their vehicle, forced them out of the vehicle, disarmed his three bodyguards and shot the Turkish engineer," the governor said. "Later they poured fuel over his body and burned him."
The bodyguards were freed although their weapons were stolen.
A Taliban spokesman said they had killed the engineer but denied burning his body, alleging this was government propaganda.
Islam forbids the burning of corpses.
Two more foreign nationals were killed in the area on Tuesday last week when a remote-controlled bomb hit their vehicle. Three Afghans also died in the blast.
The Taliban government was toppled in late 2001 in a US-led military operation after they failed to hand over Osama bin Laden, the alleged mastermind of the September 11, 2001 attacks on the United States.
The Taliban was toppled by US-led
forces in 2001
They have since been waging a deadly insurgency with help from bin Laden's al-Qaeda and other fighters, mostly against foreign and Afghan troops.
In more violence on Sunday, a policeman and a Taliban fighter were killed in a gunfight in southern Helmand province, an official said.
Helmand, the top producer of Afghanistan's illegal opium crop, has been the scene of the worst attacks blamed on the Taliban.
About 3,300 British troops are due to be deployed to the province soon to help fight the Taliban and the drugs trade.
They will be part of a Nato force of peacekeepers expanding from its current operations in the north and west of the country into the south and eventually the east, taking over from a separate US-led coalition.
The International Security Assistance Force (ISAF) is expected to eventually number between 23,000 and 25,000 troops, Nato's military commander in Europe, US General James Jones, said on Friday.