At least nine people were killed and dozens of others wounded by two suspected suicide blasts at a Sufi shrine in the southern Pakistani city of Karachi on October 7.
The explosions hit the Abdullah Shah Ghazi shrine on its busiest night of the week, as people were leaving evening prayers.
The Sufi community in Karachi declared three days of mourning, during which all Sufi shrines in the city will be closed.
Officials said security was also being tightened at mosques and other sensitive areas in Karachi.
Meanwhile, President Asif Ali Zardari blamed the attacks on "those who want to impose an extremist mindset and lifestyle upon our country," but said the government would not be deterred.
Pakistani shrines and mosques have frequently been the target of Islamist militant groups in recent years.
In July, twin suicide bombers attacked a Sufi shrine in the eastern city of Lahore, killing more than 40 people and wounding nearly 200.
compiled from agency reports