It comes after Taliban gunmen killed 149 people, including 133 children, in a school massacre in the northwestern city of Peshawar last week.
Six militants have been hanged since Friday amid rising public anger over the slaughter.
Around nine gunmen stormed the army-run school on 16 December taking teachers and students hostage and killing them in classrooms.
After the deadliest terror attack in Pakistani history, Prime Minister Nawaz Sharif ended the six-year moratorium on the death penalty, reinstating it for terrorism-related cases.
“Interior ministry has finalised the cases of 500 convicts who have exhausted all the appeals, their mercy petitions have been turned down by the president and their executions will take place in coming weeks,” a senior government official told AFP on condition of anonymity.
Of the six hanged so far, five were involved in a failed attempt to assassinate the then-military ruler Pervez Musharraf in 2003, while one was involved in a 2009 attack on army headquarters.
Police, troops and paramilitary Rangers have been deployed across the country and airports and prisons put on red alert as the executions take place and troops intensify operations against Taliban militants in northwestern tribal areas.
Mr Sharif has ordered the attorney general’s office to “actively pursue” capital cases currently in the courts, a government spokesman said.
The decision to reinstate executions has been condemned by human rights groups, with the United Nations also calling for it to reconsider.
Human Rights Watch described the executions “a craven politicised reaction to the Peshawar killings” and demanded that no further hangings be carried out.
Pakistan began its de facto moratorium on civilian executions in 2008, but hanging remains on the statute books and judges continue to pass death sentences.
Before Friday’s resumption, only one person had been executed since then – a soldier convicted by a court martial and hanged in November 2012.