"They have all studied from reputed institutions and one of them who is the mastermind (Tahir Hussain Minhas) of the Ismaili killings has personally met Osama bin Laden and Aiman al-Zawahari in the past," a senior police officer told PTI.
He said that the four militants are linked to a sleeper cell of al-Qaeda.
Sindh Chief Minister Syed Qaim Ali Shah and Interior Minister Chaudhary Nisar Khan said the militants have confessed their involvement in the May 13 attack in which militants donning police uniforms gunned down 45 Shia Ismaili Muslims, including 16 women in country's volatile Karachi city, claimed by the dreaded ISIS terror group.
Minhas alias Sain Nazir alias Mota-matriculate has been involved in terror activities since 1998.
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"He (Minhas) is a trained terrorist who has expertise in making bombs and using arms such as RPG-7 and Kalashnikov," the officer said.
Aziz, a BBA graduate, has been involved in terrorist activities since 2009.
"He also produced Jihadi literature and provided funds for terror activities in the city," the police official said.
The Chief Minister has said the police have seized three Kalashnikov rifles, seven 9mm rifles, five grenades, seven laptops, explosive material and terrorism literature.