Unidentified gunmen pulled over a car and shot dead a UN driver in western Afghanistan, police and the United Nations said on Wednesday.
Another UN employee and a government official fled the attack in the Balabuluk district of Farah province late on Tuesday, UN spokesman Aleem Siddique told the agency.
The victim was named as Yar Mohammad, a driver for UN-HABITAT, the United Nations Human Settlements Programme.
"An unknown number of gunmen in a car stopped a UN-HABITAT vehicle carrying three people. The driver was brutally shot by unknown assailants," Siddique said.
"The two passengers fled as the assailants drove off," he added.
The two passengers who survived were a UN-HABITAT employee and a government official from the ministry of rural development.
Provincial police chief Sayed Agha Saqib blamed the "enemies of peace and reconstruction of Afghanistan."
The term "enemies of Afghanistan" is commonly used by Afghan officials to refer to the remnants of the ousted Taliban who were forced from power in late 2001 by a US-led offensive.
The incident came a day after officials said that a Colombian aid worker and two Afghan colleagues employed by a French organisation, Madera, were kidnapped in central Afghanistan.
Attacks on aid workers are common in Afghanistan, although the war-shattered country's west is less affected by the spiralling Taliban-led insurgency that has destabilised the south and east.