At least 22 people were killed on Sunday in a bomb blast in the crowded market of a garrison town in northwest Pakistan's Khurram tribal agency, near the Afghan border.
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 23 people, who were in serious condition, were taken to Peshawar Lady Reading Hospital in Army helicopters.
No group has yet admitted to carrying out the attack but a sectarian motive was suspected, as most people in Parachinar are from Pakistan's Shia minority.
Khurram agency has a history of sectarian violence between Shia and Sunni Muslims, and agreements to calm tensions between the communities have not been implemented.
Several Taliban-affiliated groups -- predominantly Shia -- are known to be active in the region.
Violence in the country overall has fallen since the Pakistani army embarked on an offensive against the Taliban and other militants in the North Waziristan agency, bordering Khurram.
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.
Deploring the loss of precious lives in the blast, President Mamnoon Hussain strongly condemned the incident and directed that the best possible medical treatment be provided to the injured.
Prime Minister Nawaz Sharif, in a separate message, expressed grief at the loss of life and property and commiserated with the bereaved families.
Sharif said "our resolve to eradicate the menace of terrorism is getting stronger with the loss of innocent lives and sacrifices of the army and law enforcement agencies".
He said the ongoing fight was an irreversible process until the scourge of terrorism was rooted out from the country.
