At least 12 people including four police were killed and seven others wounded in the brazen assault late Monday staged by militants disguised in police uniforms, they said.
"A total of 243 prisoners have escaped, six of them were later arrested by police," senior government official Mushtaq Jadoon told private TV channel ARY News, adding that "30 among the escaped prisoners were hardcore militants".
The attack targeted the Central Prison in Dera Ismail Khan, a city in Khyber Pakhtunkhwa Province, close to the lawless tribal regions bordering Afghanistan where Taliban and Al-Qaeda-linked insurgents are active.
A security official said the jail held up to 5,000 prisoners including some 300 militants involved in attacks on security forces and sectarian killings.
Jadoon said the fighters had planted dozens of explosive devices in the jail and 14 of them had so far been defused.
"Police and other law enforcing agencies are busy in clearing the jail," he said, adding authorities have imposed a curfew in the city and asked residents to stay at home.
"Through media, we appeal to the people to stay at home. It is to avoid any damage if army, police and paramilitary take any action," he added.
Jadoon said around 50 to 60 militants managed to enter the jail as others fired rockets from outside.
"First they destroyed a police armored vehicle parked at the front gate," he said, adding that two policemen were killed in the initial rocket attack.
In a reminder of the enormous security challenges facing Pakistan, the violence broke out just hours before the nation's lawmakers are expected to vote for the country's new president.
The new head of state will replace outgoing President Asif Ali Zardari, who is ending a five-year term. His party lost May's general elections and his successor is likely to be Mamnoon Hussain, a close ally of Prime Minister Nawaz Sharif.
The Taliban have claimed responsibility for the jail attack.
"Some 150 Taliban, including 60 suicide bombers, attacked the Central Prison and managed to free about 300 prisoners," Taliban spokesman Shahidullah Shahid told AFP by telephone.
Pakistan is battling a Taliban-led domestic insurgency that has killed thousands of civilians and security personnel since 2007.
BA/BA