Dan McNorton said, "Around 600 non-Afghan staff will be temporarily relocated."
"The only people who will remain are regarded as essential staff.... This is to ensure the safety of all our staff in Afghanistan."
According to him, nearly all the 600 employees will leave the country and small number could be relocated within Afghanistan
The decision would be regularly reviewed and was expected to be effective for "a number of weeks."
The move comes eight days after a Taliban attack on a hostel in Kabul in which five UN workers were killed.