More than 600 protesters blocked a major highway in Islamabad for several hours during the morning rush hour, burning tyres and causing long delays.

In Peshawar, about 200 demonstrators smashed windows at the main Lady Reading Hospital, where many of the victims were treated, and blocked the main Grand Trunk road.

At All Saints Church, more than 100 people chanted slogans demanding justice and attacking the national government for failing to protect Christians.

They also had harsh words for the cricketer-turned-politician Imran Khan, whose Pakistan Tehreek-e-Insaf party runs the provincial government in northwestern Khyber Pakhtunkhwa province. Protesters shouted abusive slogans against Imran Khan, who they accuse of being soft on militants, including regular chants of, "Imran is a dog".

Khalid Shahzad, who lost five family members in the church attack, said: "Imran Khan and his senior deputy have failed to protect Christians at their praying centres. The government of Khyber Pakhtunkhwa and Imran Khan are just making slogans. There is nothing practical [to protect us]. They do not have any sympathy for minorities."

Paul Bhatti, president of the All Pakistan Minorities Alliance and who was minister for national harmony in the last government, said the attack was the deadliest ever targeting Christians in Pakistan. He added that 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, but we fear that this is the beginning of a wave of violence against the Christians," said Danish Yunas, a Christian driver wounded in the blast. "We fear there will be more of this in the future."

The 400 or so worshippers were exchanging greetings after the service when the bombers struck. The walls were pockmarked with ball bearings that had been packed into the bombs to cause maximum carnage.

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 linked to the Pakistani Taliban 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.

But yesterday, the main spokesman for the umbrella Tehreek-e-Taliban Pakistan group said the Taliban was not responsible. "Whenever we carry out an attack we claim it, but the Taliban is not involved in this attack," Shahidullah Shahid said.

"It was an attempt to sabotage the atmosphere of the proposed peace talks."

Prime Minister Nawaz Sharif has called several times for peace talks with the Taliban and two weeks ago won backing from the country's main political parties.

But he said on Sunday the government was "unable to proceed further" with talks in the wake of the church attack.