[9][10] Numerous Pakistani government and media reports have also claimed the backing of a foreign hand, mainly India's Research and Analysis Wing (RAW), behind the attack.

[1][16] A number of analysts trace the origins of sectarian violence in the country back to the Soviet war in neighbouring Afghanistan, during which armed fundamentalist groups surfaced in the region.

[18] A total of six gunmen (including two disguised in police uniform) on three motorcycles stopped the bus shortly after its departure from the Safoora Chowrangi area of Karachi.

Ismailis tend to be a peaceful, progressive and largely non-political community in Pakistan, with notable contributions to the country's education and health sectors.

[18] Jundallah, a banned Sunni splinter militant group associated with the Tehrik-i-Taliban Pakistan, claimed responsibility for the shooting, and vowed to carry out more attacks on Shia Muslim minorities.

[3] Jundallah, which in 2014 vowed allegiance to the Islamic State of Iraq and the Levant, left pro-ISIL propaganda leaflets near the scene.

[23] However, the Pakistani Foreign Office ruled out the involvement of ISIL, stating "The terror outfit has no footprints in Pakistan but our security forces are alert to meet any threat".

There have been allegations among Pakistani media and government sources of the involvement of Indian intelligence agency Research and Analysis Wing (RAW) in the attack.

[9][29] RAW has been blamed by Pakistani authorities in the past, especially for its alleged involvement in the insurgency in Balochistan, via intelligence networks in neighbouring Afghanistan.

"[9][30] According to Pakistan Today, initial investigations briefed to the Chief of Army Staff included the "strong possibility" of RAW involvement.

[35] Chief of Army Staff General Raheel Sharif cancelled his three-day visit to Sri Lanka and went to Karachi to assess the situation.

[36] General Sharif also telephoned Prince Aga Khan, leader of the Ismaili community, during which he expressed his condolences, stating: "Our heart goes out for the bereaved families.

[38][39] Aga Khan IV, the Spiritual Leader of the Ismaili Muslims, expressed his "shock and sadness" and said that it represented a "senseless act of violence against a peaceful community".