Protests in Lahore by members of Pakistan's Christian minority have turned violent, with police using tear gas and water cannon on the crowds.
Demonstrators smashed cars and threw stones in response to the bombing of two churches by a Taliban splinter group on Sunday.
The protests came as the death toll in Sunday's attacks rose to 17.
Christians make up less than 2% of Pakistan's population and many are among its poorest people.
There are reports at least three people were injured in Monday's protests when they were run over by a speeding car trying to get away from the violence.
Pakistan's Interior Minister Chaudhry Nisar Ali Khan called for calm and urged protesters not to take the law into their own hands as they blocked roads and burned tyres in Youhanabad, Lahore's largest Christian neighbourhood.
Protests have also been taking place in the eastern cities of Faisalabad, Sargodha and Gujranwala.
Christian missionary schools around the country are closed as Pakistan observes a day of mourning.
- Make up 1.6% of Pakistan's predominantly Muslim population
- Majority are descendents of those who converted from Hinduism under the British Raj
- Most converted to escape their low-caste status and many are among the poorest in Pakistan
- Targeting of Christians fuelled by strong anti-blasphemy laws and anger over US-led war in Afghanistan
Protests in Youhanabad were initially peaceful, with adults and children carrying crosses and raising banners saying "Stop killing Christians" as they marched towards St John's Church and Christ Church, the scenes of Sunday's blasts.
But they later turned violent, with demonstrators pelting the police with stones and smashing vehicles, said Rana Sanaullah, an official with the ruling PML-N party.
The BBC's Shaimaa Khalil in Lahore says the riots are a rare show of anger from a community that has long been vulnerable and unprotected. Christians in Pakistan feel they have regularly been targeted by extremists and abandoned by their government, she says.
"We are proud to be Christians here but the way we are treated... is beyond our understanding," Arcene Anthony, a sister at St John's, told the BBC.
Interior Minister Chaudhry Nisar Ali Khan called the assaults "an inhuman act of terrorism".
Attacks against Christians in Pakistan are not uncommon, analysts say. Some are related to Pakistan's controversial anti-blasphemy laws.
But Sunday's was the first large-scale attack on the community since 22 September 2013, when the bombing of a Peshawar church killed more than 120 people, in what is thought to be the deadliest attack on the country's minority.