The attack on All Saints church in the northwestern city of Peshawar after a service on Sunday, claimed by a Taliban faction, is believed to be the deadliest ever to target Pakistan's small Christian minority.
Doctor Arshad Javed of the city's main Lady Reading hospital told AFP the death toll had risen to 81 overnight, including 37 women. A total of 131 people were wounded.
Christians demonstrated in towns and cities around Pakistan, including Islamabad, Lahore, Karachi, Peshawar and Faisalabad, to protest against the violence and demand better protection from the authorities.
In Islamabad more than 600 protesters blocked a major city highway for several hours during the Monday morning rush hour, causing long tailbacks, an AFP photographer said.
Paul Bhatti, the president of All Pakistan Minorities Alliance (APMA) who was minister for national harmony in the last government, told AFP the attack was the deadliest ever targeting Christians in Pakistan.
"We are very clear that it was an incident of terrorism. Christians are not the only target of terror, whole Pakistan is a victim of terrorism," said Bhatti, whose brother Shahbaz was assassinated in 2011 for speaking out against the country's blasphemy laws.
"Terrorist are targeting everyone, they are beasts. The time has come for Pakistan to take an action against them."
He added Christian schools would close for three days of mourning.
Senior Peshawar police official Najeeb-ur-Rehman said security around churches in the city would be stepped up, but survivors of the bombing spoke of their fears of further violence.
"We had very good relations with the Muslims -- there was no tension before that blast, but we fear that this is the beginning of a wave of violence against the Christians," Danish Yunas, a Christian driver wounded in the blast, told AFP.
"We fear there will be more of this in the future."
Prime Minister Nawaz Sharif strongly condemned the "cruel" attack, saying it violated the tenets of Islam and Pope Francis also spoke out against the violence, calling it "a bad choice of hatred and war".
The small and largely impoverished Christian community suffers discrimination in the overwhelmingly Muslim-majority nation but bombings against them are extremely rare.
The 400 or so worshippers were exchanging greetings after the service when the bombers struck, littering the church with blood, body parts and pages from the Bible.
The walls were pockmarked with ball bearings that had been packed into the bombs to cause maximum carnage in the busy church.
Sectarian violence between majority Sunni and minority Shiite Muslims is on the rise in Pakistan but Sunday's bombings will fuel fears the already beleaguered Christian community could be increasingly targeted.
A faction of Pakistan's umbrella Taliban movement, Junood ul-Hifsa, claimed responsibility for Sunday's attack, saying it was to avenge US drone strikes on Taliban and Al-Qaeda operatives in the country's tribal areas along the Afghan border.
"We carried out the suicide bombings at Peshawar church and will continue to strike foreigners and non-Muslims until drone attacks stop," Ahmad Marwat, a spokesman for the group, told AFP by telephone.
Prime Minister Sharif has called for peace talks with the Taliban and two weeks ago won backing from the country's main political parties.
But after a week that began with the militants killing an army general in the northwest and ended with the church attack, some are questioning whether dialogue is the right approach.
Khyber Pakhtunkhwa is a deeply conservative province bordering the tribal districts along the Afghan frontier which are home to Taliban and Al-Qaeda militants.
Provincial lawmaker Ghauri said there were about 200,000 Christians in the province, of whom 70,000 lived in Peshawar.
Only around two percent of the country's population of 180 million are Christian. The community complains of growing discrimination.
Christians have a precarious existence in Pakistan, often living in slum-like "colonies" cheek-by-jowl with Muslims and fearful of allegations of blasphemy, a sensitive subject that can provoke outbursts of public violence.
In the town of Gojra in Punjab province in 2009, a mob burned 77 houses and killed seven people after rumours that a copy of the Islamic holy book the Koran had been desecrated during a Christian marriage ceremony.
Rimsha Masih, a Christian girl who was arrested for alleged blasphemy last year, fled to Canada with her family in June after the charges were dropped.