The United Nations has said it is not permanently pulling out of Afghanistan, but has had to take action to protect its staff.
Around half of the UN's team are being moved out of the country because of concerns for their safety.
It follows last week's attack by Taliban militants in the capital, Kabul, in which five foreign UN staff were killed.
A UN spokesman said the organisation would relocate about 600 of its 1,100 international staff.
UN Spokesman Aleem Siddique said the evacuations would not disrupt its operations in the country.
Siddique said the UN staff would return in three to four weeks after its security measures are changed.
The head of the UN mission in Afghanistan, Norwegian diplomat Kai Eide, denied that the evacuation amounted to a withdrawal from Afghanistan.
‘We are not pulling out and will not pull out,’ he said.
‘The UN is putting in place immediate additional security measures for its international and Afghan staff.
‘We will do what we can to avoid disruption of our work,’ he added.
The UN has around 5,600 staff in Afghanistan, about 80% of whom are Afghans, and the relocations will affect around 12% of its total deployment.
The decision would be reviewed regularly and was expected to be effective for a number of weeks while additional security is being put in place.
In a statement, the United Nations said it was ‘fully committed to helping all of Afghanistan's people, as it has been for more than half a century’.
‘Every effort will be made to minimise disruption to our activities while these additional security steps are being taken,’ it said.
The move comes eight days after Taliban suicide gunmen stormed a Kabul hostel in a dawn attack that killed five UN workers.
In last week's attack, Taliban suicide bombers hiding explosive vests under police uniforms entered a guest-house used by UN staff, killing five foreigners and prompting a security review by many of the international agencies in the country.
A second round of the presidential election, which was to be held on 7 November, was cancelled after President Hamid Karzai's only opponent withdrew, citing insufficient safeguards against fraud.
