KARACHI, Pakistan — Gunmen stormed a bus carrying Shiite Muslims in southern Pakistan and ordered them to bow their heads before being shot, killing at least 45 people Wednesday in the latest attack targeting the religious minority.
Who carried out the attack in the port city of Karachi wasn't immediately clear, as a Pakistani Taliban splinter group and an Islamic State affiliate both claimed it. However, some Taliban fighters have pledged their allegiance in recent months to the extremist group that now holds a third of Iraq and Syria in its self-declared caliphate.
"These are the people who are extremists, who are terrorists," provincial police chief Ghulam Haider Jamali said of the assailants. "These are the same people who have been doing terrorism before."
The bus was on the outskirts of the city traveling to an Ismaili Shiite community center when six gunmen boarded it, Jamali said. The attackers ordered the passengers to bow their heads and not look up before opening fire at close range, investigator Khadim Hussain said.
Shell casings at the scene suggested the gunmen used both pistols and machine guns in their attack before fleeing on three motorcycles, police said. Jamali said the attackers killed 45 people, including 16 women, and wounded 13.
Qadir Baluch, a security guard at a nearby building, said he heard the gunshots and saw at least one of the militants wearing a police uniform.
The attack riddled the bus with bullet holes, but its wounded driver still could drive it to a nearby hospital, said Mohammad Imran, a guard there. Imran said when he got on the bus later he saw blood still seeping across its seats and floor. Blood stained Imran's own hands and uniform.
"I hardly saw any survivor," he said.
Prime Minister Nawaz Sharif, who rushed to Karachi, condemned the bus attack, calling it "an attempt to create chaos."
"Terrorists have chosen a very peaceful and patriotic community to target in order to achieve their nefarious designs," Sharif said.
United Nations Secretary-General Ban Ki-moon also condemned the attack, saying Pakistan must "take swift measures aimed at effective protection of religious minorities in the country."
Pamphlets found nearby the site of the attack claimed an Islamic State affiliate carried it out, calling it revenge for the killing of fellow fighters in Pakistan, Syria, Iraq and Yemen, police officer Najeeb Khan said.
Meanwhile, a man describing himself as a spokesman for a splinter faction of the Pakistani Taliban called Jundullah, or Army of God, claimed responsibility for the attack in a call to The Associated Press. The man, who identifies himself as Ahmad Marwat and has conveyed similar claims in the past, said "infidels were the target."
The Taliban and other Sunni militant groups long have had a presence in Karachi. Sunni extremists view Pakistan's minority Shiites as apostates and have targeted them in the past, though attacks on the Ismaili branch have been rare.
Wednesday's attack was the deadliest in Pakistan since December, when Taliban militants killed 150 people, mostly young students, at an army-run school in Peshawar.
The Pakistani Taliban have been fighting for more than a decade to overthrow the government and impose a harsh version of Islamic law, killing tens of thousands of people.
The Islamic State group, meanwhile, has demanded the allegiance of the world's Muslims and has drawn radicals for its bloody propaganda videos, featuring mass killings or beheadings. Some in Pakistan have made their own filmed killings. A Pakistani government letter written in December and later obtained by the AP warned local officials that the Islamic State group claims the support of up to "12,000 followers" in northwest Pakistan.
This is second time pamphlets attributed to Islamic State group have been found at the site of an attack in Karachi, government counter terrorism officer Umar Khitab said. The Islamic State group in the so-called "Khorasan Province," the affiliate named in the pamphlets, later posted the claim of responsibility on Twitter, according to the SITE Intelligence Group, a U.S. firm that monitors terror groups.
At the Karachi hospital that took in the wounded, panicked relatives wept and tried to comfort teach other. Soofia Ali, 18, who lost her parents, wailed outside an intensive care unit where her wounded brother clung to life, unable to speak to those around her. A relative consoled her, asking her to pray.
Shahzad reported from Islamabad. Associated Press writers Munir Ahmed in Islamabad and Ishtiaq Mahsud in Dera Ismail Khan, Pakistan, contributed to this report.