"First there was a small blast followed by a big blast" on Friday morning outside the court in a Christian neighborhood near Warsak Dam in the Khyber tribal region, 20 kilometers (12 miles) northwest of Peshawar City, said Haris Habib, a local rescue officer.
There were lawyers, police officers and civilians among the victims, the official added.
Shortly afterwards, the Taliban-linked Jamaat-ul-Ahrar militant group in Pakistan claimed responsibility for the assault.
Taliban spokesman Ehsanullah Ehsan said there were "several deaths" in the attack.
