Bomber targets minibus carrying security personnel in garrison city of Rawalpindi.
Supporters also gathered in Larkana and in the adjacent village of Naudero, where the Bhutto family ancestral home is located.
Pakistani officials meanwhile said the government will hold talks with the Taliban after the group announced a ceasefire.
A Taliban spokesman in South Waziristan tribal district said a day earlier that Baitullah Mehsud, the key suspect in the murder of Bhutto, had ordered an indefinite truce.
Hamid Nawaz, the interior minister, said: “There is no announced ceasefire, there is a de facto ceasefire between militants and government troops. Both sides are currently holding the fire.”
Nawaz said a tribal council, or jirga “comprising representatives of the government and tribal elders will be formed to negotiate peace but I cannot give you any timeframe in this regard”.