Twenty people were drugged, tortured and then hacked to death with knives and clubs in a Pakistani shrine on Sunday.

Abdul Waheed, 50, the shrine's custodian and two accomplices have been charged with the murder of 20 worshippers at the Sufi shrine to Mohammad Ali Gujjar in Punjab province.

One survivor told police Waheed had called followers into his chamber one by one and drugged them.

He and his companions then killed them with a dagger and a stick.

Deputy police commissioner Liaquat Ali Chatta said: 'As they kept arriving, they were torturing and murdering them.'

Rescue workers gather around the bodies of worshippers allegedly killed by Abdul Waheel

Officials are investigating whether the killings were an attempt to assert control of the shrine

The victims were apparently drugged before the brutal killings and some are reported to have been found naked.

Pervaiz Haider, a hospital doctor, said most of the victims were hit on the back of the neck.

He told Reuters: 'There are bruises and wounds inflicted by a club and dagger on the bodies of victims.'

The victims were apparently drugged before being hacked to death with knives and daggers

The shrine was built about two years ago on the grave of Ali Mohammad Gujar, a local Sufi religious leader.

Police investigators said Waheed had said during questioning that he killed his disciples because he believed they had fatally poisoned Gujar two years ago, and feared they were planning to do the same to him.

Among the dead was the son of Gujjar, who some locals claim is the rightful heir of the shrine.

A local government official said Waheed might have had mental health problems and had acted violently towards his followers previously.

He told The Guardian: 'The suspect appears to be paranoid and psychotic, or it could be related to rivalry for the control of shrine.'

Rana Sanaullah, the law minister for the Punjab provincial government, said an initial investigation found Waheed had a collection of followers who would regularly visit the shrine and face torture in the name of religious cleansing.

They were accustomed to seeking spiritual cleansing by removing their clothes.

Mr Waheed had reportedly been asking worshippers to visit the shrine, then attacked them

The alarm was raised by an injured woman who was among several victims who managed to escape.

Children had also witnessed the violence through a door. Adult devotees then attacked the suspects before police rushed to the shrine and arrested Waheed and his accomplices.

Local police offical Nusrat Ali said the trio 'will be presented at a local court today' for a hearing.

Local rescue service official Mazhar Shah said Mr Waheed used to meet devotees once or twice a month and used violence to 'heal' them

Pervaiz Haider, a hospital doctor, said most of the victims were hit on the back of the neck

Injured Pakistani men recover in hospital after an attack on a Sufi shrine by three suspects, including the shrine's custodian

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.

Sufis believe in saints to 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.

But visits to shrines and offers of alms for the poor - and cash to custodians - remains a very popular custom. Many believe this will help get their prayers answered.

'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.

Extremist groups such as ISIS have carried out major attacks on Sufi shrines because they consider them heretical.

A view of the cordoned off Sufi shrine where 20 worshippers were tortured and killed

In February 90 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 in an attack claimed by ISIS.

Shrines are soft targets for attack.

In remote and rural areas they are far from medical aid.