"This Consulate expects the Pakistani government to firmly deal with the issue by identifying and punishing the perpetrators of this anti-humane act," the Iranian Consulate General said in a statement on Monday.
The diplomat stated that the "horrible terrorist" attack on March 3 was "an effort aimed at sowing discord in the Muslim community of Pakistan and an action against Muslims and the entire humanity."
It added that the perpetrators of this violent attack must stand justice.
In another statement, the Iranian Foreign Ministry strongly deplored the Sunday terror attack on Shiite Pakistanis that left at least 45 dead in Karachi.
The ministry expressed sympathy with the relatives of the victims, and added that such terrorist moves serve the divisive policies of the enemies of Pakistan's Muslim nation and harm the country's interests.
The statement called on the Pakistani government and prominent religious figures in the country to take proper actions to prevent similar attacks in future.
The statement also asked the international community to play a serious role in an all-out fight against terrorism which is considered as a threat to all nations.
Police officials announced later on Sunday that at least 45 people have been killed by the bomb explosion in Karachi.
The blast in the mainly Shiite Muslim area of Abbas Town destroyed several buildings and set others on fire. Some reports spoke of a second explosion.
No group has yet said it planted the bomb, which went off near a mosque as worshippers left evening prayers.
