A bomb blast in a park in the eastern Pakistani city of Lahore on Sunday has killed at least 72 people and wounded at least 300.According to estimates, at least 8,000 people were at the park when the blast happened. The attack was the worst so far this year in a country grimly accustomed to atrocities, and will further undermine fractious inter-religious ties in the Muslim-majority nation. Witnesses described children screaming as people carried the injured in their arms, while frantic relatives searched for loved ones.

Rescue spokeswoman Deeba Shahbaz said the death toll had risen to 72 Monday, with 29 children among the dead. Senior police official Haider Ashraf confirmed the number, adding that most of the dead were Muslims. Punjab's chief minister Shahbaz Sharif announced three days of mourning and pledged to bring the perpetrators to justice, said Zaeem Qadri, a spokesman for the provincial government.Pakistani security officials inspect the scene of a suicide bomb attack in Lahore, Pakistan, 27 March 2016. (EPA Photo)A Taliban splinter group named Tehreek-e-Taliban claimed the attack. The group is said to be the Pakistani wing of the terrorist organization."We carried out the Lahore attack as Christians are our target," Ehansullah Ehsan, spokesman for the Jamaat-ul-Ahrar faction of the Tehreek-e-Taliban Pakistan, told AFP by telephone on Monday from an undisclosed location. He said the group would carry out more such attacks, vowing to target schools and colleges alongside government and military interests.Many of the injured are in a critical condition, Salman Rafiq, a health adviser to the chief minister of Punjab province said.The explosion took place near the children's rides in Gulshan-e-Iqbal park, local police chief Haider Ashraf said. He said the explosion appeared to have been a suicide bombing, but investigations were ongoing.Relatives of the victims of a suicide bomb blast cry outside a hospital in Lahore, Pakistan, 27 March 2016. (EPA Photo)The area was crowded with Christians celebrating the Easter holidays, and many families were leaving the park when the blast occurred, Ashraf said.Ashraf said the park was manned by police guards and private security guards. "We are in a warlike situation and there is always a general threat but no specific threat alert was received for this place," he added.Footage broadcast on local television stations showed chaotic scenes in the park, with people running while carrying children and cradling the wounded in their laps.A witness, not identified by name on Pakistan's Geo TV station, said he was heading toward a ride with his wife and two children when he heard a huge bang and all four of them were thrown to the floor.

Lahore's top administration official Muhammad Usman said around 100 of the wounded were either treated at the scene or quickly discharged. He said a further 180 had been admitted to hospital.

Javed Ali, who lives opposite the park near the city centre, said Sunday's blast shattered the windows of his home.

"After 10 minutes I went outside. There was human flesh on the walls of our house. People were crying, I could hear ambulances," he said.

Schools and other government institutions were open Monday but three days of mourning have been announced in Punjab province, of which Lahore is the capital.

Facebook activated its safety check system after the blast so people could tell friends and relatives they were safe, but a glitch meant notifications were sent to people all over the world. The company later apologised.

Prime Minister Nawaz Sharif expressed "grief and sorrow over the sad demise of innocent lives".

The US labelled the bombing "cowardly" while Russian president Vladimir Putin branded it a "crime".

Pakistan's Nobel Peace Prize winner Malala Yousafzai tweeted: "Pakistan and the world must unite. Every life is precious and must be respected and protected."

The Vatican condemned the attack, calling it "fanatical violence against Christian minorities", and UN Secretary General Ban Ki-moon called for Islamabad to protect religious minorities.

Christians make up an estimated 1.6 percent of Pakistan's 200 million people and have long faced discrimination.

Twin suicide attacks against churches in Lahore killed 17 people in March last year, sparking two days of rioting by thousands of Christians.

The country is still scarred by a Taliban assault on a Peshawar school in 2014 that killed 150 people, mostly children.

A military operation targeting insurgents was stepped up in response. Last year the death toll from militant attacks fell to its lowest since the Pakistani Taliban were formed in 2007.