KABUL: The US-funded reconstruction of the Kabul-Kandahar highway is vaunted by the government as a symbol of Afghanistan's recovery from 23 years of war.

But the murder of a Turkish engineer working on the road and the kidnapping of another by suspected Muslim militants on Friday is a reminder of the security challenges the country faces as it nears another critical test this summer - elections.

An insurgency against foreign troops, Afghan forces and aid groups in Afghanistan has made much of the country a no-go zone. It is also complicating efforts to register 10.5 million voters ahead of presidential polls scheduled for June or July.

The US military said on Saturday small civilian-military teams posted in three locations along the vital Afghan highway would try to keep "terrorists" off the road, but there were no plans to boost the number of US forces along the route.

An American infantry company of around 100 soldiers has been posted for more than a month in Zabul, the most unstable of the provinces through which the artery passes. There are also civilian-military teams in Zabul, Ghazni and Kandahar.

But the road is 482km long, and work has been disrupted by a series of kidnappings and killings by militants.

"We condemn this attack," US military spokesman Lieutenant-Colonel Bryan Hilferty told a news briefing in Kabul. "We think it's an example of the terrorists' desperation when they continue to attack the people who come to Afghanistan."

A Turkish engineer was killed and another kidnapped in the Shah Joy district of Zabul province on Friday. An Afghan guard was also killed and a translator kidnapped. The attack follows the kidnapping of two Indian workers in December and of a Turkish contractor in October. All were later released. A number of Afghan guards, soldiers and deminers have also been killed along the route.

Louis Berger Group, the American company overseeing the road's renovation, had a helicopter shot at by a gunman near Kandahar in February. The Australian pilot was killed and two passengers - a Briton and American - were wounded.

The Taliban's deputy commander of operations in the south of Afghanistan, Mullah Sabir Momin, said by satellite telephone from a secret location that the Turkish engineers were involved in spying against the ousted Islamic militia.-Reuters