The blast was heard over a significant area of the city close to parliament and various government offices.
It brought fears of a strike by militant bombers after a day of heavy clashes between militants and government troops in the northwest of the country.
"A gas boiler blew up in a house," said the emergency service official. "No casualties."
Almost 60 people were killed and scores wounded in clashes in the northwest, near the Afghan border, on Friday, according to police, security officials and a militant spokesmen.
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