"It was a powerful blast," said local administration chief Ajmal Khan. "At least six rooms were demolished."
A mosque and several houses were also damaged.
Saturday was the Muslim holy day Eid Milad-un-Nabi, which celebrates the prophet Mohammed's birthday.
Elsewhere gunmen fired on an Eid Milad-un-Nabi procession in the northwestern district of Dera Ismail Khan, killing one and wounding several others.
Two or three men were hiding behind trees before they opened fire on people who were carrying banners and reciting hymns.
The procession was organised by a Sunni Muslim party. It is not known who was behind the attack.
In another rally in Faisalabad, in the central Punjab province, four marchers were wounded by gunshots and a mob attacked a police station and torched dozens of cars and motorbikes.
More than 3,000 people have died in bombs in Pakistan since July 2007.