"We received terror alert today about a possible prison break in four major prisons of the province," a senior prison official in Khyber Pakhtunkhwa who saw the alert told AFP on conditions of anonymity."The letter had warned of a massive prison break," he added.He said the Home Department has advised prison officials to collaborate with the local police to increase security around all high profile inmates charged with terror-related offences.Another senior intelligence official confirmed that a threat warning had been issued.He said there are a number of high profile terrorists on death row in four prisons in the province who might be executed within days."The terrorists might attack prisons to free their comrades on death row, especially after the end of moratorium on death sentence," he told AFP requesting anonymity.Nawaz announced on Wednesday an end the ban on the death penalty in terror-related cases after an attack a military-run school in Peshawar claimed by the Taliban killed 148 people, mostly schoolchildren.The assault in Peshawar is one of the deadliest attack to strike the country, and has shocked the nation.Political and military leaders have vowed in response to wipe out the extremist insurgency that has killed thousands of ordinary Pakistanis in recent years.Pakistan imposed a defacto moratorium on civilian executions in 2008, though hanging remains on the statute book and judges continue to pass the death sentence.Only one person has been executed since then, a soldier convicted by a court martial and hanged in November 2012.Rights campaign group Amnesty International estimates that Pakistan has more than 8,000 prisoners on death row, most of whom have exhausted the appeals process.In July last year dozens of heavily armed Taliban fighters freed nearly 250 prisoners, including hardcore militants, during a sophisticated overnight attack on a jail in the northwest.It was not the first time either the Afghan Taliban or their Pakistani counterparts have claimed prison breaks. In April 2012, nearly 400 prisoners escaped from a jail outside Bannu during a similar insurgent raid.