meeting of political parties convened by the Assistant Political Agent of Khyber Agency to discuss a code of conduct for upcoming polls.
Some reports suggested the militants carried out the attack to free prisoners being held in a jail within the complex.
No group claimed responsibility for the attack though such incidents are usually blamed on the banned Tehrik-e-Taliban Pakistan.
Peshawar and other parts of Khyber-Pakhtunkhwa province have witnessed a sudden surge in violence by the Taliban.
Provincial Chief Minister Ameer Haider Khan Hoti narrowly escaped an attempt on his life by a Taliban suicide bomber last week.
The Taliban recently offered peace talks to the federal government but refused to disarm. They have said they will continue their attacks till a peace deal is finalised.