"The police force in the area has tactically retreated from the district after days of fighting," he told Reuters news agency, saying there were no signs of reinforcements despite repeated requests.
Jamaluddin Badar, provincial governor of Nuristan, said Afghan forces had retreated in order to prepare for a counter attack.
"We have lost the district to the Taliban ... but will push them back soon," he said.
Zabihullah Mujahid, a Taliban spokesman, confirmed the group now controlled the district.
"The Taliban flag is flying high in the district centre and it is a huge victory for our fighters," he told Reuters by telephone from an undisclosed location.
"Our fighters are still clearing other villages and looking for Afghan police and their supporters."
In July last year, some 300 Taliban fighters seized the same district headquarters before being pushed back by Afghan and international troops three days later.
In October 2009, Taliban fighters killed eight US soldiers after storming another remote outpost in the Kamdesh district of Nuristan province.
Since the withdrawal of foreign troops from Kamdesh and Barg-e-Matal districts, Afghan police say the area is under immense threat from anti-government forces coming from Pakistan.
US forces announced plans to withdraw from the area as part of US commander General Stanley McChrystal's strategy to focus his forces on population centres in Afghanistan.