SEHWAN, Pakistan (AP) -- Pakistani forces killed and arrested dozens of suspects in sweeping raids as the death toll from a massive suicide bombing by the Islamic State group that targeted a famed Sufi shrine the day before rose to 88 on Friday.
The terror attack — Pakistan's deadliest in years — stunned the nation and raised questions about the authorities' ability to rein in militant groups despite several military offensives targeting militant hideouts.
It also threatened to drive a deeper wedge between Pakistan and Afghanistan. Islamabad quickly lashed out at Kabul, saying the bombing was masterminded in militant sanctuaries across the border in Afghanistan.
Underscoring tensions, Pakistan fired a blistering round of artillery shells into Afghan territory on Friday and shut down the Torkham border crossing, a key commercial artery between the two neighbors.
Afghan police chief Gul Agha Roohani in eastern Nangarhar province told The Associated Press the artillery assault began on Friday morning, although there was no immediate confirmation from Pakistan.
Afghan President Ashraf Ghani condemned the shrine attack. "Sufis always preach peace and brotherhood among people," he said in a statement, adding added that "terrorists once again proved that they have no respect for Islamic values."
Meanwhile, raids overnight across Pakistan targeted militant hideouts and led to shootouts with insurgents that left at least 39 suspects dead, according to three Pakistani security officials who spoke on condition of anonymity under regulations.
Most of the operations were carried out by the paramilitary Rangers. In one raid, troops killed 11 suspects at a militant hideout in the port city of Karachi. In another, the Rangers came under fire as they were returning from Sehwan, the town in southern Sindh province where the shrine bombing took place, and killed seven of the attackers.
Other raids took place in northwestern Pakistan and also in the eastern province of Punjab. The officials said a total of 47 suspects were arrested.
In Thursday's attack, the suicide bomber walked into the main hall at the Lal Shahbaz Qalandar shrine in Sehwan, and detonated his explosives among a crowd of worshippers, initially killing 75. At least 20 women and nine children were among the dead.
On Friday, authorities raised the death toll to 88 after some of the critically wounded died. The Sindh provincial health department said a total of 343 people were wounded in the attack but that most were discharged after treatment while 76 still remain in hospitals.
The Islamic State group, claiming responsibility for the attack in a statement circulated by its Aamaq news agency, said it targeted a "Shiite gathering." The Sunni extremist group views Shiites as apostates and has targeted Pakistan's Shiite minority in the past. It also views Sufi shrines as a form of idolatry.
The Sehwan shrine, which reveres a Muslim Sufi mystic, is frequented by the faithful of many sects of Islam but the majority of the worshippers are usually Shiite Muslims.
Raja Somro, who witnessed the attack, told a local TV network that hundreds of people were performing a spiritual dance known as the "dhamal" when the bomber struck.
Local TV showed graphic footage of the aftermath of the blast, with wounded worshippers crying out for help and the floors covered with shoes, blood and body parts. Women cried and beat their chests in grief.
Prime Minister Nawaz Sharif vowed that security forces would track down the perpetrators, according to Pakistani state TV.
"Each drop of the nation's blood shall be avenged, and avenged immediately," Pakistan's army chief, Gen. Qamar Javed Bajwa, said in a statement.
The U.S. State Department condemned the attack and offered its support to Pakistan in bringing the perpetrators to justice.
The attack was the deadliest in Pakistan after the Dec. 16, 2014 assault on an army-run school in Peshawar that killed 154 people, mostly schoolchildren. A Taliban-linked group, Jamaat-ul-Ahrar, claimed responsibility for that attack.
Pakistan has been at war with the Taliban and other extremist groups for more than a decade. In recent years it has launched major offensives against militant strongholds in the tribal regions along the border with Afghanistan, but insurgents have continued to carry out attacks elsewhere in the country.
The Islamic State group has been expanding its presence in Pakistan in recent years and has claimed a number of deadly attacks, including a suicide bombing at another Sufi shrine in November 2016 that killed more than 50 people.
The government has downplayed the IS affiliate, insisting that only a small number of militants have pledged allegiance to the group.
Afghanistan and Pakistan have long accused each other of failing to crack down on militants who operate along the porous border.
Also Friday, the Pakistani military handed over to Kabul a list of 76 suspected "terrorists" allegedly hiding in Afghanistan, demanding they be captured and extradited to Islamabad. A statement from the military says the list was given to Afghan officials at the Pakistani army's sprawling headquarters in the garrison city of Rawalpindi.
The military did not specify who was on the list, but it has long claimed that the head of Pakistani Taliban, Mullah Fazlullah, and other militants are hiding on Afghan soil with the purpose of fomenting violence inside Pakistan.
In Sehwan, police fired tear gas on Friday and swung batons to disperse a rally of several hundred protesters who demanded justice for the victims and better security measures from the government. The crowd set fire to a car before the police broke up the rally.
At one of the funerals that got underway Friday, relatives consoled the wailing mother of Zeeshan Ali, a 13-year-old who died in the shrine blast. Ali's uncle, Shoukat Ali, said he was devoted to his nephew and raised him since he had no children of his own.
"I raised him like my own child ... and they took him from me," he said.