Pakistan's Interior Minister Chaudhry Nisar Ali Khan warned of further attacks after a Taliban assault on a school in Peshawar last week left 141 dead, including 132 children.
In response to the attack Pakistan lifted a moratorium on the death penalty and has so far executed six militants, with more expected to follow.
None of those hanged has anything to do with the December 16 school rampage, and some Pakistani commentators have said the executions are intended to divert attention from the failure to satisfy public demands to find the killers.
The Taliban have issued statements promising to stage more attacks around Pakistan in retaliation for the executions of any of their fighters.
Security has been tightened around major prisons, reflecting fears that the militants, who are fighting to topple the government and set up a state governed by Islamic law, might try to attack jails and free inmates.
Addressing reporters in Islamabad, Khan warned the population to be vigilant against potential threats.
“After this incident and after the hangings that have been carried out, and also because of the military operations that our armed forces are carrying out in that region, we are receiving intelligence from across the country that the militants are getting ready for another savage and inhuman counter attack. All of us need to be on the alert,” said Khan.
Christians across Pakistan held special services on Sunday to pray for the victims of the school attack.
In Lahore's St. Mary's Cathedral, hundreds of candles were lit, and hymns sung by a solemn congregation.
Earlier in the day, in the port city of Karachi, hundreds of Christians gathered outside a local church to condemn the school attack.
Many among the crowd, some wearing Santa Claus costumes, held placards reading “United we stand in grief and sorrow.”
“We are going to celebrate our upcoming Christmas festival with utter simplicity because we are together with our Pakistani brothers in this hour of grief and pain. The entire Christian community is mourning today. We stand with the Pakistani armed forces who are fighting against terrorism,” local priest Reverend Muntazir Gill told reporters.
In Islamabad, Christian families lit candles in the compound of St. Thomas Church and prayed for the victims of the attack and their families.
“As human beings we have been so greatly saddened by this incident that we do not have the words to describe our grief. The children who were killed were angels; they have awakened people by their sacrifice,” said Babar Masih, a local Christian.
The school assault was the deadliest militant attack ever in Pakistan. Footage of terrified children and classrooms awash with blood has provoked a wave of revulsion in a country mostly inured to daily violence.
The Pakistani Taliban, who are allied with but separate from the Afghan Taliban, said the school attack was revenge for the offensive against them and they accused the military of killing civilians in remote areas where journalists are forbidden to go.
Since the school attack, the government has promised that Pakistan would not discriminate between different militant factions, trying to draw a line under years of support for some groups seen as useful in Pakistan's confrontation with India and in achieving Pakistan's aims in Afghanistan.