Islamabad, Pakistan (CNN) At least six people are dead after a suicide blast targeted police posted outside the Data Darbar shrine in Lahore, Pakistan, officials told CNN.

Police did not say how many are injured. The investigation is ongoing, the district Commissioner of police for Lahore said.

Pakistan's Prime Minister Imran Khan's office released a statement "strongly condemn(ing)" the attack.

"(Khan) has expressed grief at the casualties and solace to the families of those who have lost their loved ones," it added. "An investigation is going to be started into this attack. The injured will receive the best care available."

Data Darbar is the largest Sufi shrine in South Asia. Wednesday marks the second day of the holy month of Ramadan, which is widely observed in Pakistan.