Pakistani authorities have vowed to hunt down the perpetrators behind an Easter Sunday bombing in the city of Lahore that killed more than 70 people and injured some 300 others.
"We will not allow them to play with the lives of the people of Pakistan," Prime Minister Nawaz Sharif said in a televised address late on March 28. "This is our resolve. This is the resolve of the 200 million people of Pakistan."
As the country began three days of mourning, Sharif said the army would launch a military operation on extremist hideouts and police will go after what he called the "cowards" who carried out the attack.
Sharif, who canceled a visit to the United States to attend a nuclear summit this week, warned extremists against using Islam to justify their violence in the overwhelmingly Muslim nation.
A Taliban splinter group claimed responsibility for the blast that ripped through crowds near a children's play area in Gulshan Iqbal Park, where many had gathered to celebrate Easter on March 27.
Jamaat-ul-Ahrar said it had targeted Christians and vowed to carry out more such attacks on schools, colleges, and other government and military interests.
The group said the attack was a "message" to Sharif, who counts the Punjab Province and its capital, Lahore, as a political stronghold.
Army chief General Raheel Sharif vowed that Pakistan "will never allow these savage nonhumans to overrun our life and liberty."
The military said on March 28 that it had carried out a series of raids in Lahore and nearby areas following the attack, arresting several suspects.
"Number of suspect terrorists and facilitators arrested and huge cache of arms and ammunition recovered," military spokesman Asim Bajwa said in a Twitter post.
He said that operations "to nab the terrorists in the aftermath of Lahore blast" are continuing.
Police said the death toll had risen to 72 on March 28, with 29 children among the dead. With hundreds injured, the toll was expected to rise.
WATCH: Scores Killed In Pakistan Park Bombing (natural sound, viewers may find some scenes disturbing)
Senior police official Haider Ashraf said the majority of the dead were Muslims, who were also in the crowded park.
Pope Francis decried what he called the "hideous, vile, and abominable" bombing against Christians, and urged Pakistani authorities to "make every effort to restore security and serenity" in the country, particularly for religious minorities.
Earlier this month, Sharif had officially recognized holidays celebrated by Pakistan's minority religions, including Easter and the Hindu festival of Holi.
White House spokesman Josh Earnest on March 28 called the bombing "grotesque."
"The fact that you have an extremist organization targeting religious minorities and children is an outrage," he said, while also noting the high number of Muslims among the victims.
The government announced three days of mourning with the national flag flying at half-staff.
Schools and markets were closed and traffic was thin on the roads across the province on March 28.
Sharif visited injured people being treated at a hospital, his office said.
"It strengthened my resolve when I met the wounded people," he said in his address. "God willing, I will not sit idle until I bring smiles back on their faces."
Earlier, Sharif had expressed "grief and sorrow over the sad demise of innocent lives."
His Indian counterpart, Narendra Modi, telephoned to say "the people of India stand with their Pakistani brethren in this hour of grief," state media reported.
UN Secretary-General Ban Ki-moon condemned the attack, calling it an "appalling" act of terrorism.
In the capital, Islamabad, security was tight on March 28 around the parliament and other strategic points to prevent riots by militant protesters who have been rallying there since the previous day.
Jamaat-ul-Ahrar, which has publicly supported the Islamic State extremist group, also took responsibility for the twin bombings of a Christian church in Lahore last year. At least 14 people were killed in those bombings.
Overall levels of militant violence in Pakistan have fallen since the army launched a major offensive against Taliban and Al-Qaeda strongholds in the northwest border areas in 2014, though militants continue to stage major attacks occasionally.