Men at a Sehwan, Pakistan, hospital mourn their relatives' deaths after a suicide attack Thursday.

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New: Pakistan says more than 100 killed in terror crackdown

ISIS affiliate in Afghanistan and Pakistan claimed responsibility for attack

Islamabad, Pakistan CNN  — 

Pakistan’s military has launched a crackdown on what it says are terrorists with ties to Afghanistan after a suicide attack on a packed shrine in the southern city of Sehwan killed at least 88 worshipers.

The number of people injured in Thursday’s attack on the famed Lal Shahbaz Qalandar shrine has climbed to 200, Fazal Pechuho, health secretary for Pakistan’s Sindh province, said Friday.

Of the dead, 24 were children ages 4 to 8. Another 16 of the victims were women, according to Dr. Zahid Hussain, a local hospital official.

Pakistani soldiers cordon off Lal Shahbaz Qalandar shrine in Sehwan after Thursday's attack.

Thousands of worshipers, including families with children, had gathered Thursday at the more than 800-year-old shrine for the Sufi ritual of Dhamal, which involves music, chanting and prayer.

The Islamic State Khorasan, ISIS’ affiliate in Afghanistan and Pakistan, claimed responsibility for the bombing in a phone call to CNN.

In response, the Pakistani military said it had shut down the border with Afghanistan, killed more than 100 terrorists and arrested many others throughout country.

Additionally, Pakistan demanded that the Afghan government turn over more than 75 people who allegedly planned, directed and supported terrorism across the border, the military said.

Pakistan military officials also called Gen. John W. Nicholson, commander of the American-led international military force in Afghanistan, to request assistance in the fight against leaders and financiers of terror groups hiding on the other side of the border.

Prime Minister calls attack ‘brutal’

In the aftermath of Thursday’s blast, the dead and injured overwhelmed the 100-bed Sehwan Hospital, Hussain told CNN.

Many patients were later transferred to bigger hospitals in other cities of Sindh province, he said.

Pakistani volunteers carry the body of a blast victim from a Sehwan hospital Friday.

The Amaq news agency, which is affiliated with ISIS, reported a suicide bomber in an explosives vest carried out the attack.

Pakistani Prime Minister Nawaz Sharif called the attack “brutal.”

“I have directed all the state institutions to mobilize all resources for rescue and relief after this brutal terror attack on Lal Shahbaz Qalandar’s shrine,” Sharif said in a statement.

Search operations in the Rawalpindi area have been stepped up, according to Inter-Services Public Relations, or ISPR, the media wing of the Pakistan armed forces. Senior law enforcement agency officials also met Friday to assess the security situation and ways to respond to the terror threat.

“Security forces and intelligence outfits have been instructed to further intensify combing and targeted operations with the aim to eliminate terrorists and sleeper cells,” an ISPR statement said.

An ‘enormous threat’

The wounded receive medical treatment Thursday at a Sehwan hospital.

In a series of tweets, Pakistani military spokesman Maj. Gen. Asif Ghafoor blamed operatives from Afghanistan for a recent spate of attacks and urged his country to remain calm.

The office of the Afghan President Ashraf Ghani said on Twitter that he “condemns (the) terrorist attack in Pakistan and terms ISIS a common enemy of Afghanistan & Pakistan.”

Sediq Sediqqi, spokesman for the Afghan Ministry of Interior Affairs, tweeted that the Islamic State Khorasan poses an “enormous threat” to both the Afghan and Pakistani people and called for the two countries to work together to eliminate the extremist group.

The Sehwan attack comes three days after a bomb exploded during a protest in Lahore, killing at least 14 people and injuring 59 more, according to government spokesman Malik Ahmad Khan.

Jamaat-ul-Ahrar, a splinter group of Pakistan’s Tehreek-i Taliban – also known as the Pakistani Taliban – claimed responsibility for Monday’s attack in a statement emailed to CNN.

CNN’s Sophia Saifi and Adeel Raja reported from Islamabad, and Ray Sanchez wrote from New York. CNN’s Laura Smith-Spark and journalist Saleem Mehsud contributed to this report.