Twenty people were hacked and clubbed to death after being tortured in a Pakistani shrine early on Sunday, according to local officials. The custodian of a Pakistani religious shrine and two accomplices have been arrested for the murder of 20 worshippers with knives and clubs, police have said.

Officials said the custodian gave the worshippers intoxicants before killing them with knives and batons. Some of the victims are reported to have been found naked. The worshippers, followers of a local Sufi leader who died two years ago, were accustomed to seeking spiritual cleansing by removing their clothes.

A number of possible motives have been suggested for the attack, which took place at the Sufi shrine to Mohammad Ali Gujjar in Punjab province. The regional police chief, Zulfiqar Hameed, said: “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.”

Another local government official, speaking on condition of anonymity, said Waheed had told the police that Muhammad Ali Gujjar, a self-proclaimed mystic turned saint who is buried at the shrine, had been poisoned two years ago. Waheed feared he might be killed too.

Officials told media they were investigating whether the killings were an attempt to assert control of the shrine, which is located 105 miles northwest of Lahore. Among the dead was the son of Gujjar, who some locals claim is the rightful heir of the shrine.

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“Abdul Waheed became custodian of the shrine two years ago. He feared that the son of the saint might remove him as custodian and take charge of the shrine himself,” Hameed told the Guardian.

He added that the chief suspect might have had mental health problems and had acted violently towards his followers previously. “The suspect appears to be paranoid and psychotic, or it could be related to rivalry for the control of shrine,” Hameed added.

Local police station chief Shamshir Joya told the Guardian: “[Abdul Waheed] called on the devotees whom he was suspecting may act against him in the rivalry over the custody of the shrine, and brutally tortured them to death. Their clothes were taken off before they were beaten and they were possibly intoxicated too.” Six of the victims belonged to the same family.

According to local police, the attack was reported when an injured woman managed to escape the shrine. After the attack, the local hospital received 20 dead victims and four injured people.

“The dead people were badly tortured with clubs and knives, mainly on their necks and backs,” said Dr Pervade Haider, chief medical officer at the hospital.

Facebook Twitter Pinterest A view of the Sufi shrine where three suspects including the shrine’s custodian killed at least 20 people. Photograph: Israrul Haq/EPA

Waheed had reportedly been asking worshippers to visit the shrine, then attacked them. “As they kept arriving, they were torturing and murdering them,” the deputy commissioner for the area, Liaqat Ali Chattha, told national television.

Local rescue service official Mazhar Shah said Waheed used to meet devotees once or twice a month and used violence to “heal” them. “Local people say that Waheed used to beat the visitors who came to him for treatment of various physical or spiritual ailments,” Shah told reporters.

Television footage showed scattered shoes, clothes, sheets and cots in the yard of the white domed shrine as police vehicles and commandos surrounded the premises.

Shabbir Gujjar, a local police officer and relative of the shrine saint, lost his son in the attack. He said his family had been devoted to the shrine for 10 years. “Abdul Waheed called my son’s family to the shrine last night, and brutally killed my son.”

The Punjab minister for religious affairs, Zaeem Qadri, said intelligence agencies, along with police and the local government, were investigating all aspects of the case. Qadri said his department managed 552 shrines in the province, but this one was not registered with it. “Investigators will also look into how this shrine was allowed to be set up on private land,” he said.

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“A case like this shows dangerous levels of ignorance, exploitation and rivalries of shrine due to booming business,” a senior police official told the Guardian.

Visiting shrines and offering alms for the poor – and cash to the custodians – remains a popular custom in Pakistan. 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.

Sufis believe in saints they say can intercede for them directly with God. They have no hierarchy or organisation, instead seeking spiritual communion through music and dance at the shrines of the saints.

Several million Muslims in Pakistan are still believed to follow Sufism, although it has been overtaken in recent decades by more mainstream versions of the faith. The victims of Sunday’s attack belonged to the Barelvi sect, which has previously been the target of anti-Sufi violence. Hardliners such as the Taliban or Islamic State have carried out major attacks on Sufi shrines because they consider them heretical.

The attack comes only days after 24 worshippers were killed at another Pakistani shrine, a Shia mosque in Parachinar, in a suicide attack claimed by Jamaat-ul-Ahrar, a splinter factions of the Pakistani Taliban.

In February, 88 people were killed and hundreds wounded in Pakistan’s southern province of Sindh when a suicide bomber blew himself up among devotees at a Sufi shrine.

Additional reporting by Waqar Gillani