Pakistani authorities have tightened security at religious locations across the country after two suicide blasts killed at least 42 people at a Muslim shrine in the eastern city of Lahore.
More than 180 people were wounded late Thursday when attackers struck as thousands of people were gathered at the Data Gunj Baksh (commonly known as the Data Durbar) shrine, the tomb of a famous Sufi saint.
Police say an investigation is underway to determine the identity of the attackers. They say one of the bombers detonated his explosives in a courtyard at the shrine and the other set off his explosives in the basement where people wash themselves before praying.
On Friday, police increased security around mosques to ensure the safety of Muslim worshipers during morning prayers. People also took to the streets of Lahore to protest the attack.
Authorities suspect Pakistani Taliban militants are behind the attack, but the militant group is denying involvement.
The United States joined Pakistani Prime Minister Yousuf Raza Gilani in condemning the attacks.
Prime Minister Gilani said the Data Gunj Baksh shrine has sentimental value to Muslims across the country, and that targeting it shows the attackers have no consideration for religion, faith or belief.
European Union foreign policy chief Catherine Ashton said the Lahore attack is yet another example of the scale of the terrorist threat and extremism in Pakistan.
The Sufi shrine is seen as a symbol of moderate Islam that is practiced by most people in the Muslim-majority nation.
A coordinated suicide attack on two mosques of the minority Ahmadi community killed 82 people in Lahore in May.