Ahmed Awad bin Mubarak, who is also secretary general of the national dialogue set up to oversee the political transition, was seized by gunmen at a checkpoint in Yemen's southern Hada district.
A statement by the Shiite Huthi militia said the kidnapping was a measure to prevent a UN-brokered agreement between the presidency and them in September "from being broken."
The chief of Yemen's national security service, General Mohammed al-Ahmadi, told reporters "talks are ongoing to secure his release."