The number of young people who have died at a makeshift nightclub in a township in South Africa's southern city of East London has risen to 20, a senior safety official said Sunday.

"The number has increased to 20, three have died in hospital. But there are still two who are very critical," head of the provincial government safety department Weziwe Tikana-Gxothiwe said on local TV.

Earlier, the police confirmed 17 deaths at the nightclub.

"We got a report about 17 (people) that died in a local tavern in Scenery Park which is based in East London," a provincial police spokesman brigadier Thembinkosi Kinana told AFP.

"We are still investigating the circumstances surrounding the incident," he added.

He said the victims were aged between 18 and 20 years.

The Eastern Cape provincial community and safety department official Unathi Binqose, speaking from the scene, ruled out a stampede as cause of death.

"It's difficult to believe it's a stampede as there are no visible open wounds to those dead," Binqose told AFP by telephone.

A regional local newspaper, DispatchLive, reported "bodies are lying strewn across tables, chairs and on the floor; with no obvious signs of injury".

Unverified pictures shared on social media showed bodies with no visible signs of injuries, strewn on the floor of the club.

Local television showed police officers trying to calm down a crowd of parents and onlookers gathered outside the club in the city, which lies on the Indian Ocean coast, nearly 1,000 kms (620 miles) south of Johannesburg.

"Parents whose children did not sleep at home are gathered here and they want to enter the tavern to look for their loved ones," said Binqose.

He said he understood the patrons were students "celebrating pens down, a party held after writing (high school) exams."