Twenty people were murdered and four others wounded at a Pakistani Sufi shrine early Sunday by men wielding batons and knives, police said.
Four women were among those killed at the Shrine of Mohammad Ali in Punjab province, according to police, who said they had arrested three suspects including the shrine's custodian.
"The 50-year-old shrine custodian Abdul Waheed has confessed that he killed these people because he feared that they had come to kill him," regional police chief Zulfiqar Hameed told AFP.
"The suspect appears to be paranoid and psychotic, or it could be related to rivalry for the control of shrine," he said, adding that the investigation was continuing.
Punjab Chief Minister Shahbaz Sharif has asked for a police report on the investigation within 24 hours, a senior government official said.
Visiting the shrines and offering alms to the poor -- and cash to the custodians -- remains very popular in Pakistan, where many believe this will help get their prayers answered.
There have been cases of people dying during exorcism ceremonies at some Sufi shrines across Pakistan, but mass killings are rare.
For centuries Pakistan was a land of Sufism, a mystical branch of Islam whose wandering holy men helped spread the religion throughout the Indian subcontinent in the 13th century.
Several million Muslims in Pakistan are still believed to follow Sufism, although it has been overtaken in recent decades by more conservative versions of the faith.
Hardliners such as the Taliban or the Islamic State group have carried out major attacks on Sufi shrines because they consider them heretical.