No one was killed or injured in the blast, which damaged windows and barriers around the building, a UN spokesman said.

It is thought to be the first car bomb attack against the UN in Afghanistan.

Kandahar is the spiritual home of the hardline Islamic Taleban movement, who ruled Afghanistan until US-led troops ousted them in 2001.

Last week, a bomb exploded outside the offices of the aid agencies, Save the Children and Oxfam in the capital, Kabul.

There were no casualties.

Staff had just left

No group has yet said it was behind Tuesday's bomb, which targeted the offices of the United Nations Assistance Mission to Afghanistan (Unama) in Kandahar's Shehr-e-Nau district.

The UN says the device was placed in an unmarked vehicle parked outside the Unama compound.

The device went off at about 1600 local time (1130 GMT), just after workers had left the building at the end of the day.

The Taleban and its sympathisers have been blamed for a series of attacks on foreign soldiers and aid workers in southern and eastern Afghanistan in recent months.

Tuesday's explosion in Kandahar comes just days after a UN Security Council delegation ended a visit to Afghanistan with a warning that the security situation must improve before aid efforts could take effect.