Forty-three members of the Ismaili Shia community were killed and 13 others injured when gunmen targeted their bus in the Pakistani port city of Karachi on Wednesday, the latest in a string of attacks on the country's minorities.
Around six to eight gunmen armed with 9mm pistols boarded the bus near Safoora Chowk area of Karachi and fired indiscriminately. The gunmen escaped after the attack on motorcycles.
A Pakistani Taliban splinter group also asserted responsibility for the attack that experts say casts doubts over the Nawaz Sharif government’s capacity to fight terrorism within the country’s borders.
Later in the day, the Islamic State group claimed responsibility, though the country has repeatedly said ISIS does not have any presence in the country.
IS said in a statement posted on jihadist Twitter accounts, "Thanks be to Allah, 43 apostates were killed and around 30 were wounded in an attack carried out by Islamic State soldiers on a bus transporting Shiite Ismaili infidels in the city of Karachi."
It was the first official claim of responsibility by the IS leadership of an attack in the Afghanistan-Pakistan region.
IS, which has seized control of large parts of Syria and Iraq, announced in January the creation of a branch in what it called "Khorasan province", encompassing Afghanistan, Pakistan and parts of surrounding countries.
Officials said 43 people were killed, including 16 women, and another 13 people were wounded.
Sixty people were in the bus, which was on its way to a place of worship for Ismaili Shias when the gunmen boarded it in a relatively deserted area on the outskirts of Karachi and sprayed the passengers with bullets.
The bus belonged to Al-Azhar Garden Colony, an Ismaili community housing project.
A senior police official told Dawn.com the attackers shot passengers in the head. Over 60 empty shells were found at the scene.
Several people succumbed to their injuries while being taken to hospital. The condition of several of the wounded was described as critical.
A security official showed AFP a copy of a torn and blood-stained pamphlet claiming responsibility on behalf of the Islamic State - the second time in as many months that such material has been discovered at the scene of an attack in Karachi.
However, the AP reported the attack was claimed by Jundullah. Ahmad Marwat, the purported spokesman of the Jundullah called the Associated Press from an undisclosed location and said "infidels were the target".
Pakistan's Shia minority has been repeatedly targeted by extremists over the past few years. Scores have died in these attacks.
The Taliban and other Sunni extremist groups, which view Shias as apostates, have long had a presence in Karachi.
At least 1,000 Shias have been killed in the past two years in Pakistan, with many attacks on the minority being claimed by the hardline Lashkar-e-Jhangvi. Wednesday's attack was the second deadliest militant strike in Pakistan this year after 62 Shias were killed in a suicide bombing in late January.
Pakistan Army chief Gen Raheel Sharif cancelled a three-day visit to Sri Lanka after the attack. Prime Minister Nawaz Sharif condemned the 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.
Prime Minister Narendra Modi too condemned the attack. He posted on his Twitter account: "The attack in Karachi is deeply saddening & utterly condemnable. Our thoughts are with the families of the deceased."
He tweeted: "We stand firmly with the people of Pakistan in this hour of grief. I wish all those injured a quick recovery."
(With agency inputs)