Ban on Sunday, March 27 called for "the perpetrators of this appalling terrorist act to be brought swiftly to justice, consistent with human rights obligations", a news agency reported.
At least 69 people were killed and over 250 injured, mostly women and children, when the blast occurred at Gate No. 1 of the public park where Christian families were celebrating Easter on Sunday.
The splinter group Jamaat-ul-Ahrar, a faction of the Pakistani Taliban, claimed responsibility for the attack and said it deliberately targeted Christians on Easter.
"We claim responsibility for the attack on Christians as they were celebrating Easter," a spokesperson for the terrorist group was quoted as saying.
"We had been waiting for this occasion... we want to convey... to the prime minister that we we have arrived in Punjab and we will reach you," it added.