A bomb exploded near the office of a regional government official in the often restive city of Peshawar early on Thursday, police officials said, but there were no immediate reports of casualties.
A wall of the district coordination officer's building collapsed after the blast, which was heard throughout Peshawar, the last major city on the route to Afghanistan.
Peshawar is also not far from Mohmand, the district where a strike by Nato-led forces at the weekend killed 24 Pakistani soldiers and plunged often uneasy relations between Washington and Islamabad to new lows.
Taliban militants have often launched suicide attacks in and around Peshawar in their campaign to topple the Pakistani government for its support of the US-led war against militancy.
The army has launched a series of offensives against the Pakistani Taliban but have failed to subdue the group, which is close to al Qaeda and is blamed for many of the suicide bombings across Pakistan, an unstable, nuclear-armed US ally.
Pakistani Taliban officials have said the group is holding exploratory peace talks with the Islamabad government.
Since the weekend strike in Mohmand, Pakistan has announced it will boycott an international conference on the future of Afghanistan in Germany next week, depriving the talks of a central player in efforts to bring peace to Afghanistan.
Pakistan has labelled that attack as a deliberate act of aggression, although that has been categorically denied by senior US military officials.