"If the government shows will, it can control this terrorism," said Hemphray. "We have been asking authorities to enhance security, but they haven't paid any heed."
Hundreds of Christians burned tires in the street in the southern city of Karachi to protest the bombing.
Pakistani Prime Minister Nawaz Sharif condemned the attack in a statement sent to reporters, saying, "The terrorists have no religion and targeting innocent people is against the teachings of Islam and all religions."
"Such cruel acts of terrorism reflect the brutality and inhumane mindset of the terrorists," he said.
Islamic militants have carried out dozens of attacks across the country since Sharif took office in June, even though he has made clear that he believes a peace deal with the Pakistani Taliban is the best way to tamp down violence in the country.
Pakistan's major political parties endorsed Sharif's call for negotiations earlier this month. But the Taliban have said the government must release militant prisoners and begin pulling troops out of the northwest tribal region that serves as their sanctuary before they will begin talks.
There are many critics of peace talks who point out that past deals with the Taliban have fallen apart and simply given the militants time to regroup.
"I don't think appeasement will work," said Farhatullah Babar, a senior leader of the main opposition group, the Pakistan People's Party. "This is a message from them that they don't believe in negotiations. If they don't, we should also stand up and fight them."
Supporters of negotiations say they are the only way forward since military operations against the Taliban in the tribal region have failed to subdue them.
Sharif defended the government's decision to push for peace talks but acknowledged the effort didn't seem to be working.
"It was not a bad thing, I think, to do a good job with a good intention," Sharif told reporters outside the Pakistan High Commission in London. "But the regret is that the thinking, the desire the government had, is not capable to make progress."
The U.S. has repeatedly demanded that Pakistan take stronger action against Islamic militants, especially members of the Afghan Taliban who use the country as a base for cross-border attacks on American troops in Afghanistan.
The U.S. has carried out several hundred drone attacks against Taliban militants and their allies in Pakistan's tribal region. The strike on Sunday took place in the Shawal area of North Waziristan, the main sanctuary for militants in the country, said Pakistani intelligence officials, speaking on condition of anonymity because they were not authorized to talk to the media.
Pakistani officials regularly decry drone attacks as a violation of the country's sovereignty, but the government is known to have secretly supported some of the strikes in the past, especially ones that have targeted Pakistani Taliban militants at war with the state.
The Pakistani and Afghan Taliban are allies, but have focused their fight on opposite sides of the border.