More than 20 churchgoers have been treated by paramedics after they were given a mystery "liquid substance" at a church service.

The service took place at the Mthatha City Hall in South Africa's Eastern Cape. According to the African News Agency, emergency services were called to the scene at a "church service gone wrong" on Thursday afternoon.

Eastern Cape Health spokesperson Sizwe Kupelo said: "It is alleged that the congregants were given a liquid substance by their pastor when they suddenly vomited and collapsed."

He said more than 20 people were treated by paramedics at the scene but they refused to be taken to hospital.

Two were later transferred to the Nelson Mandela Academic Hospital, where a police spokesman said they were in a critical condition.

The minister who is said to have administered the substance, Prophet Pumzile Topi, has fled and is being sought by police.

A police spokesman, Colonel Mzukisi Fatyela, said a criminal case had not yet been opened. However, he added: "This does not mean a case won't be opened, we are communicating with the doctors and they still need to determine if this substance was poisonous or not."

While details of the incident are still unclear, it follows a recent case in which another South African pastor was widely condemned for spraying his followers with Doom insecticide to 'heal' them. Lethebo Rabalago, a self-proclaimed prophet, shared photos on Facebook that showed him spraying Doom into the faces of his congregation at the Mount Zion General Assembly in the far north of South Africa.

Rabalago is among a number of South African pastors famed for their controversial practices.

Photos posted on social media last year showed Penuel Mnguni of End Times Disciples Ministries feeding live snakes into the mouths of his congregants.

He was arrested and charged with animal cruelty, though was later bailed and believed to have continued the practice.

Vigilantes then burned the tent Mnguni used for worship meetings.