At least 20 people were killed on Sunday in a bomb blast in an army cantonment in the tribal region of Pakistan, the media reported.
Amjad Ali Khan, the political administrator of the area, said 55 people were injured in the blast, Dawn reported.
The bomb blast took place at around 12.30 p.m. in the bustling Sadar market of Parachinar cantonment in Khurram Valley, an official said.
A Bomb Disposal Squad official said: "It was a timed-device bomb. Around 30 to 35 kg of explosives were used in the blast."
Security sources said two suspects have been taken into custody from the blast site.
The injured were shifted to a nearby hospital from where as many as 18 people, who were in serious condition, were taken to Peshawar Lady Reading Hospital in Army helicopters.
No militant group has claimed responsibility for the attack yet.
Khurram is one of the most sensitive tribal areas as it borders three Afghanistan provinces and at one point was one of the key routes for the movement of militants across the border.
The agency is adjacent to North Waziristan where Operation Zarb-i-Azb is in progress against the Tehreek-i-Taliban and other insurgent groups.
Parachinar is the administrative headquarters of the agency near the Afghan border.
It is a small garrison town developed by the British army in the foothills of Spin Ghar or Safed Koh (White Mountain) in mid-1895.
