Officials said Pakistani Taliban militants stormed the Central Jail in Dera Ismail Khan late Monday and freed 247 inmates, killing at least five policemen, four inmates and two private security guards and setting off more than 25 explosions in the process, Dawn News reported.
Khalid Abbas, inspector general for jails in Khyber Pakhtunkhwa, told Dawn News fighting was ongoing inside the prison and offered no information about other casualties.
Abbas also told Dawn prison officials had received a threatening letter concerning the attack.
Security officials said a search for the escaped prisoners was under way and the area surrounding the prison was under curfew.
The heavily armed members of the banned Tehrik-i-Taliban Pakistan attacked the prison from different sides before entering.
TTP spokesman Shahidullah Shahid claimed responsibility for the attack, telling Dawn News about 100 militants participated in the assault, including a number of suicide bombers.
The prison houses Taliban and militants from banned sectarian groups. Jail authorities said at least 5,000 inmates were in the facility, near the volatile South Waziristan Agency, which is home to TTP and al-Qaida militants, Dawn News said.
Officials said at least 45 high-profile militants were housed in the jail. Among the inmates was TTP commander Adnan Rashid, who gained notoriety by writing a letter to teenage education activist Malala Yousufzai, shot in the head by the Taliban last year in an assassination attempt. Rashid told Malala he wished the attack hadn't occurred but that she was targeted for speaking against the Taliban.